If you use Tumblr, you're probably going to want to bake me things, just sayin'...
Followr is a Tumblr app that allows you to perform mass updates on your following list. I proposed it to the peeps at Missing e and fyeahroleplayingrabbit, but the creators pitched hissy fits at the suggestion of making it so easy to follow and unfollow a list of people. Well, tough cookies, bitches. I'm releasing it anyway. It's really useful for role players, in particular and is such a time saver.
I'll eventually be adding some more functionality, but for right now, you can grab a list of who you follow, grab a list of who follows you, or update your following list via lists of follows and unfollows.