BookTV.org
Here's an oxymoronic concept: Book-TV. And yet they have some interesting reviews and resources.

BookPage
They have a wide variety of recent reviews, nicely categorized and up to date.

Complete Review
They don't review a lot of books, but they are very comprehensive in what they do review. The cool thing is that they link to other reviews (good and bad) of the same books.

Guardian Unlimited - Books
Guardian Unlimited bills itself as "the best daily newspaper on the world wide web." Their books section is stellar.

NY Times - Books
I like reading the NY Times Book Review on Sunday, consequently I like their site. Unfortunately, to get anywhere, you have to create an account. Fortunately, it's free and relatively no-hassle.