Both of them scour the Recently Changed list at weblogs.com and pick up links to books.
Weblog Bookwatch has lists of recently reviewed books, shows you which weblogs have reviewed the books, and which other books those blogs reviewed. Bookwatch collects links to Amazon, Powells, and Barnes and Noble.
AllConsuming.Net does a similar search, but prioritizes its lists based on recently mentioned books, so it’s more of a zeitgeist-tracking tool for those who want to keep up with blog fashion. Also lets you publish a pretty list of books to read, with pictures.
For hours of surfing delight. I’ve been addicted for years to Amazon surfing; start with a subject, look for related books based on recommendations, reviews and lists; and build a list of books to read. Then again, I’ve been addicted for many more years to libraries and bookstores; the vice hasn’t changed, only the medium.