Okay, I have tried
LibraryThing in the past, thought I had an account, but couldn't track down which email/username I have used....
In any event, I re-upped for a new account, and poked around a bit. It's a great idea, I just don't have the patience to put my current books into it. I'm just remembering that I used it last year while I was helping a friend scope out potential publishers and agents for her children's chapter book--I created a "library" of several books of similar style to see what else might turn up and who published them. Maybe I created an account for her rather than for me...that would explain it!