LibraryThing is topic #11 in the Learning 2.0/23 Things training.
LibraryThing is rather like a noncommercial version of Amazon.com. You can explore it to find good books to read by searching user-assigned tags and reading user reviews. Unlike Amazon, the section titled LibraryThing Recommendations is worth the price of admission (which is free!).
Although I've had a LibraryThing account for a while, I haven't put it to good use.
I used to keep a reading log, but I stopped that when the library catalog added a reading history feature to user accounts. I thought it was a step forward because I could access it anywhere. However, some of the items in my reading history have disappeared because they have been withdrawn from the Library's collection.
I've realized LibraryThing is a better substitute for my reading log. I can access it anywhere, no items will disappear, and I can read my annotations as well as those of others.