yeah, they're called fuckyeah tumblrs where they're dedicated to one thing. like http://fuckyeahtwilightsucks.tumblr.com, for example, is dedicated to stuff that's anti-twilight.
Uh.. Uh.. Russel Brand trumps both! (: Tumblr is seriously only a time-waster. You follow people who post cool pictures or funny quotes or nonsense and you spend hours on hours looking at pictures and laughing and doing nothing. you can post pictures, videos, text, quotes, conversations and links. It's very addicting.
China Teacups; my sis informed me that it's quite addictive :)
go in peace dru.; well, that's a cool thing to do with it. I also heard there's a lot of pages for bands and books and stuff. At least I know there's supposed to be a Harry Potter one.
I use mine for quotes, pictures I make, pictures of band boys, to post funny things, to post snippets from upcoming stories, to rant, to make fun of Sarah Orzechowski [Brendon Urie's girlfriends]. Mine's pretty bandom based.
Tumblr is mainly used for inspiration, you post things that intrigue you. Its loved for many reasons, and will soon become addictive if you stick to it. :]