I've been collecting abstract looping GIFs. Mainly from sites like 30000fps.com and Protobacillus. The animations you see in my current avatar and banner are from those sites, but there's a bunch out there on Tumblr, also. You might have also noticed them being used for the Stalkers RPG. They work really well for that too!

They're a ton of fun to work with and ever since I figured out how to nicely incorporate them into graphics, I've enjoyed working with them. I have no clue how they're made (I've never used Abobe After Effects but apparently that's the program to do it in), but I have like 600+ of them now stockpiled. The good thing is the animations are short, so there's not too many frames to have to plug in and it doesn't create huge file sizes either, but they look really cool!