I am a member of Shelfari, GoodReads, LibraryThing and Paperback Swap. I don't go on that much anymore but I try to keep my books updated on each site.
Shelfari:
Batgirl (batgirlZKE@aol.com)
GoodReads:
BatgirlZKE@aol.com
LibraryThing:
ZombieKIllerEx
PaperbackSwap:
MintyFreshKittn
For some reason, the sites won't add all my books. I currently have 1912. You can see them all here (along with the Books I Read):
Same Bat time, Same Bat channel