Bookseer is like many "what should I read next" websites, except it is impressively simple. Just type a title and author into their fun interface, and it gives reading suggestions based on Amazon.com and Librarything.com data.
Of course, the suggestions will only be as good as the data. But I like that it's building on something already available, and automatically updated, rather than relying on manual edits. And it's simple, free, creative, and doesn't require an account.