Excluding GoG of course.

Here's one off the bat: freemusicarchive.org Has ton's of free creative commons licensed music you can download.

Dammit!

Well, there's the obvious ones like YouTube and Facebook (although I only use Facebok so I can stay in touch with people or invite larger groups of friends easily - or get invited, obviously).

One of my favourite pages is probably Newgrounds. I mostly use it to upload my own audio but there's also a lot of hilarious and sometimes surprisingly intelligent animations. Oh yeah, and also all audio is published under a creative commons license there, people don't use it enough if they need music for their projects.

Also I love the webcomic Cyanide & Happiness. Actually I prefer their shorts but unfortunately they create new ones rather rarely.

Edit: Oh yeah, also: for news I prefer Spiegel Online (in German, obviously)

NeoGAF
reddit
Superhero Hype

For the UK, http://www.thedailymash.co.uk/

Science Hobbyist for science projects and what not.
Project Gutenberg for free ebooks.