Humble Store is having an End of Summer Sale that will last till 22 September. Aside the discounts mentioned below, they will also be giving free games. For today, the free game is a Steam key for Warlock - Master of the Arcane (though I personally had no success getting it so far. Edit: Finally got it!). As for the discounts:

Age of Empires III: Complete Collection -75%/€9.24 (Steam, Windows)
Amnesia: The Dark Descent -77%/€4.02 (DRM-Free/Steam, Windows/Mac/Linux)
Among the Sleep -25%/€14.99 (DRM-Free/Steam, Windows/Mac/Linux)
Batman: Arkham Asylum GOTY Edition -75%/€4.99 (Steam, Windows)
Euro Truck Simulator 2 -80%/€3.99 (Steam, Windows/Mac/Linux)
Gone Home -33%/€10.49 (DRM-Free/Steam, Windows/Mac/Linux)
Kerbal Space Program Early Access -40%/€14.99 (Steam, Windows/Mac/Linux)
Murdered: Soul Suspect -70%/€11.99 (Steam, Windows)
NIGHTS Into Dreams -75%/€1.99 (Steam, Windows)
Nihilumbra -80%/€1.39 (DRM-Free/Steam, Windows/Mac/Linux)
Psychonauts (FLASH SALE) -92%/€0.79 (DRM-Free/Steam, Windows/Mac/Linux)
Samurai Gunn -50%/€5.99 (DRM-Free/Steam, Windows)
Scribblenauts Unlimited -75%/€4.99 (Steam, Windows)
The Bridge -90%/€0.89 (DRM-Free/Steam, Windows/Mac/Linux)
The LEGO® Movie - Videogame -75%/€6.99 (Steam, Windows)
The Swapper -79%/€2.49 (DRM-Free/Steam, Windows/Mac/Linux)
The Wolf Among Us -60%/€9.99 (Steam, Windows/Mac)

All the above discounts will last for 2 more days with the exception of Psychonauts, which will last for 12 more hours.
Edit: Batman Arkham Asylum GOTY, Euro Truck Simulator 2, Gone Home and The Swapper will actually last for 2 weeks.

New batch of Steam Week Long Deals

- Book of Unwritten Tales (both parts, regular, deluxe editions and the collection) -90%
- Planets Under Attack -90%
- The 39 Steps -90%
- Iron Sky Invasion -90%
- Septerra Core -85%

along many others

Indie Gala “Every Monday” Bundle

$1.89 before price increases

Stonerid (win, steam)
Memories of a Vagabond (win, steam)
Five Nights at Freddy’s (win, steam)
Eschalon: Book I (win/mac/linux, steam)
Eschalon: Book II (win/mac/linux, steam)
Me and Postapocalypse 2: Scraping (win, desura

Well, that was quick.

Sorry, info was already posted.

By the way, if you got a key (As I did thanks to pigdog and Grargar!) notice this in the email:

Interesting. Thanks for the heads-up.

I saw that, I hope it isn't a new trend. I assume it is Humble doing the expiration on their end, and not some new expiration put in place by Valve.

It's a freebie. I can understand if the devs don't want people hoarding keys for later.

Tonight on Humble Flash Bundle!

<span class="bold">The Humble Flash Bundle: So Cute!</span>

PWYW
Girls Like Robots (DRM-Free/Steam, Windows/Mac/Linux)
Toki Tori 2+ (DRM-Free/Steam, Windows/Mac/Linux)

$1
Triple Town (Steam, Windows/Mac)

$8
Where is My Heart? (DRM-Free/Steam, Windows/Mac)
Woodle Tree Adventures (DRM-Free/Steam, Windows/Mac/Linux)

Includes soundtracks for Toki Tori 2+, Where is My Heart? and Woodle Tree Adventures.

I agree and what they are using it for I completely agree with. However I don't want my bundle links expiring in the future, so just a preemptive pessimistic statement :).

On Humble Bundle more titles are being added to the sale.

Just an example, but Monaco: What's Yours Is Mine seems to be -90% for the next 14 days.

Ah, ain't that a cute bundle! :D

Bought it as i had Triple Town and Girls Like Robots on my Steam wishlist. ^^

They don't want resellers to abuse this and have a large amount of keys to resell later on.

Lol, wasn't Woodle Tree Adventures free in some website a few days ago? Indiegala maybe? Weird choice for the higher tier...