Sorry for the necro, but I feel these links would be interesting to share:

Plugin that adds a bunch of quality of life improvements to Steam:
https://augmentedsteam.com/
Also fetches information from Is There Any Deal (mentioned by the OP)

There's also SteamDB's plugin, which also adds more useful functions to the Steam: https://steamdb.info/extension/
SteamDB is a site that grabs all the technical information from Steam that's publicly available and shows in a more user-friendly way.

This script lets you filter posts in Steam Community's home feed:
https://github.com/ZeroUnderscoreOu/SteamActivityFilter

This one lets you mass wishlist DLCs on Steam:
https://greasyfork.org/en/scripts/22104-steam-dlc-wishlister/code

Plugin for checking if a game on Steam is also on subscription services, e.g. Gamepass or EA Play:
https://aligueler.com/GamePass/

True dark mode script for Steam:
https://userstyles.org/styles/167253/true-dark-mode-for-steam-web-client
This one requires a plugin like Stylus.

Script for showing all titles on GOG in a grid view and that adds better filtering/sorting options:
https://github.com/ghorint2t/scripts/blob/master/goggamesdatagridview.user.js
According to their support, using this script should be fine.

Ad blocker, might be needed in some official key sellers:
https://github.com/gorhill/uBlock#ublock-origin

Violentmonkey for installing and using some of the scripts I bring:
https://github.com/violentmonkey/violentmonkey

Stylus, also needed for some scripts: https://add0n.com/stylus.html

Script to help sorting Steam's wishlist (since the default options are pretty bad):
https://gist.github.com/Luckz/79d35bfe77f42fd8689965adbd3c0bab/raw/SteamWishlistSortingHelper.user.js

Facebook Container, since their tracking/data hoarding goes far beyond their own site, to the point some legit stores are used as means to help with their tracking:
https://addons.mozilla.org/pt-BR/firefox/addon/facebook-container/

Modified dlls to remove the tracking function of Unity games released after 2017:
https://github.com/DerPopo/UABE/tree/2.2stabled

ArchiSteamFarm/ASF, a tool for managing your account and idling games:
https://github.com/JustArchiNET/ArchiSteamFarm

Another idler, but more simple and made exclusively for Android:
https://play.google.com/store/apps/details?id=com.steevsapps.idledaddy

GOGDB, kinda like SteamDB, but for GOG games:
https://www.gogdb.org/

GOG DB Integration so you can quickly open a game's GOGDB page from their GOG page:
https://www.gogdb.org/gogdb.user.js

Playnite, which, as a video game library manager, is a lighter, more stable, compatible with more stores and open source version of GOG Galaxy:
https://playnite.link/download.html
The biggest drawback is that it only works on Windows (apparently, it doesn't work properly with Wine).

Barefoot Essentials, which adds some quality of life improvements for GOG's site:
https://www.gog.com/forum/general/barefoot_essentials_2_gogcom_enhancement/post1801

Steam games you can play without the Steam client:
https://www.gog.com/forum/general/steam_games_you_can_play_without_the_steam_client/post1

Epic Games Store (EGS) games you can play without Epic Launcher:
https://www.gog.com/forum/general/epic_store_games_you_can_play_without_the_epic_launcher/post1

Itchio giveaways mega thread:
https://old.reddit.com/r/FreeGameFindings/comments/p0ik3q/itchio_mega_thread_10/

gogrepo.py, for downloading stuff from your GOG library more easily:
https://www.gog.com/forum/general/gogrepopy_python_script_for_regularly_backing_up_your_purchased_gog_collection_for_full_offline_e

Threads for tracking games that are at risk of getting delisted:
https://www.gog.com/forum/general/games_at_risk_of_being_removed_from_gogs_catalog_tracking_thread
https://steamcommunity.com/groups/games-at-risk/discussions/0/1696045708664604450/
https://steamcommunity.com/groups/RemGC/discussions/9/1736595131052961774/

Threads and sites for tracking games that include ROMs:
https://www.gog.com/forum/general/rom_based_gog_games_compatible_with_third_party_emulators_thread
https://retropie.org.uk/forum/topic/10918/where-to-legally-acquire-content-to-play-on-retropie
https://steamcommunity.com/app/1118310/discussions/0/1643168364654032851/
https://legal-roms.fandom.com/wiki/Legal_ROMs_Wiki
https://legalroms.miraheze.org/wiki/Main_Page

Threads for games with DRM on GOG and games without even though people would expect them to:
https://www.gog.com/forum/general/drm_on_gog_list_of_singleplayer_games_with_drm
https://www.gog.com/forum/general/lists_games_that_need_galaxy_for_multiplayer_and_the_ones_that_dont
https://www.gog.com/forum/general/drmfree_multiplayer_list_of_games_that_actually_are_100_drmfree

List of DRM-free video games digital distributors:
https://www.gog.com/forum/general/list_of_drmfree_video_games_digital_distributors

On a similar note, there's several legitimate old DOSgaming websites for those looking around for the good ole' stuff that GOG so often overlooks these days.

ClassicDosGames (known as RGB) and Dosgaming both have filters by license if you're that kind of purist.

By the way, about ITAD, there's a beta version with some neat features not present in the original version of the site:
https://new.isthereanydeal.com/

And worth noting that, according to one of the site's devs, they try to bring only legit deals, so they don't track G2A, Gamivo, Kinguin and so on on their site.

How Long To Beat, Handy to find out how long a game could potentially take to finish (possibly before a purchase), and has headings and times for various play styles too.


EDIT: BTW, you can opt-out of the cookie rubbish that is displayed on entering the site by clicking 'More Options' then 'Opt Out All' buttons...

Zelda II: The Adventure of Link

The Legend of Zelda: A Link to the Past

The Legend of Zelda: Link’s Awakening

??????

They're all games with Link(s).

Not directly gaming related but it will impact the way you use your gaming computer.

- https://www.virustotal.com/
Before visiting any new link it is wise to test the link for viruses and malware.
- https://themarkup.org/blacklight
Next step is to scan the site for tracking scripts and tracking cookies.

Remember prevention is key in any security environment so a healthy PC is a healthy gaming PC.

Useful gaming links.

- https://www.indiegamebundles.com/
Site that updates daily with great bundle offers and free games.
- https://www.retroarch.com/
Great front end for emulators, game engines and retro filters.
- https://trilarion.github.io/opensourcegames/index.html
Open Source Games List
- https://www.radmin-vpn.com/
Play LAN games online by making a VPN to simulate a local network, better than Hamachi or Gameranger.
- https://bigboxcollection.com/#CollectionOverview
A site with scanned Big Box Games generated in 3D form.
- https://longplays.org/home.php
A longplay is a play-through of a computer or video game, created with the intent of completing it as fully as possible, mainly for the purposes of nostalgia, preservation, and possibly as a walkthrough.
- https://wireframe.raspberrypi.org/issues
A free Video Game magazine like the old times in physical and free pdf format.

Okay, but why not Parsec, which is purpose built?

Talking about scripts and trackers, besides the anti-tracker tools posted by me previously and by lixicus, these tools may be helpful too:

NoScript - Blocks pretty much any script.
Link: https://noscript.net/getit

Privacy Badger - A tracker blocker.
Link: https://addons.mozilla.org/pt-BR/firefox/addon/privacy-badger17/

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Does Parsec support LAN over the net or just couch coop? If it's the latter, then, from what I understood, Parsec and the VPN tool lixicus mentioned do two different things.

From what i've seen Parsec doesn't seem gaming related. Radmin was built with LAN games in mind, tough i still prefer doing my own VPN servers and generating certificates manually and sharing it only with friends that i trust.

DOSBox - Emulator for DOS games
https://www.dosbox.com

ScummVM - Emulator for many game engines
https://www.scummvm.org

D-Fend Reloaded - Frontend for DOSBox (Site in german, but software available in multiple languages)
http://dfendreloaded.sourceforge.net/index.html

Dragon UnPACKer - Tool to extract resources (audio, graphics, videos) from many games
https://en.www.elberethzone.net/dragon-unpacker.html

Game Extractor - Tool to extract resources (audio, graphics, videos) from many games, free version available
https://www.watto.org/game_extractor.html

FRAPS - Game screenshot and video capture tool, limited free version available
https://www.fraps.com

Legendary - Open Source Epic Games Launcher
https://github.com/derrod/legendary/releases

Smacker Video & Bink - Player for Bink (.bik) and Smacker (.smk) video files used in many games
http://www.radgametools.com/bnkdown.htm

Pixelmusement / Ancient DOS games (YouTube) - Video reviews of old DOS games
https://www.youtube.com/user/Pixelmusement/playlists

Games with Adventure Game Studio engine (AGS) - Many free games
https://www.adventuregamestudio.co.uk/site/games

ScummVM Music Enhancement Project - Replacement of original MIDI music with enhanced music for games for use with ScummVM engine
https://www.pixelrefresh.com/content/scummvm-music-enhancement-project

UnExoticA - Music and remixes from Amiga games
https://www.exotica.org.uk/wiki/UnExoticA

Werbespiel Archiv - Advertising games, site in German
https://werbespiel.blogspot.com

Not this one. It's way outta date. Last release was in 2013. I'd suggest
ShareX,
OBS, or
Mangohud. And I'd rather suggest DOSbox Staging for the technological advantages.

Just saw it mentioned elsewhere, so just throwing PCem here as well, since this thread moved from links to programs. It's no longer being developed though, so the Dec 2020 version should be the last, unless someone else will take it over.

poooh like, a facebook group where he can learn to sim Amouranth or Alex Zedra to name a few, while staying in touch of course with the hottest game and hardware news and of course something like Linus his video's where he can learn anything about everything..... That seems to be most important for new gaming life.... for myself... i'm already so pro that i reverted back to the most plain of builds one can imagine only to find atlantis ... or that proverbial pot of gold at the other side of the black hole