to keep all these people in business…

I mean you have:
Readerware
suggested by bev and looks a lot like Collectorz but for a penny more has a free scanner. No clue which came first 😉 or what is different.

Collectorz
being pimped by angiew which runs 39.99.

Byron
which I have seen mentioned in many places and know AAR uses and is about 129? last I checked.

Fictiondb
which I am thinking of getting and need to decide fast since my trial ends soon and I think erika is happy with. It is 29.99 for the year w/a free book.

Librarything
that i know nicole uses and does seem the best price at $10 a year.

And this is just the ones I know about. Who knew there were so many anal readers in the world ;).