I tried this and absolutely love it! Must have tool as i'm making my degree work home..
Here's couple of good thingies (i try to post more later..):
Productivity starts from suitable wallpaper. This is the best wallpaper site i've ever seen. You can actually get addicted browsing there!
More textures (was this mentioned yet?):
Webtreats, icons, textures, photoshop resources:
HDRI, textures, panorama stuff:
This isn't free but..
"Oloneo® PhotoEngine™ is the only HDR and Raw processing software offering digital photographers full control over light and exposure in real-time, as if they were still behind the lens."
Just check it out, it's freaky stuff!
Flash game creation software, looks kinda awesome, also there's iStencyl (you probably can guess what's that for):
NOX Renderer. Free.
Game Design Document Template:
The link is huge. Just write "baldwin game design document" in google..
Depth of Field Calculator: