I'll keep MediaFire because it still seems okay, and I'll go ahead and add Box because Koh recommended it and it seems relatively popular.
I removed Imageshack per Nick's post. Photobucket seems okay for now, but if it still does the auto-resizing thing then that's annoying. The verdict is out on TinyPic for now, but I'm leaning towards removing it. I still don't know anything about 2shared.
Thanks for the information, guys!