Epicreads.com is a website and online community for young adult books and authors. There's contests, forums where things can be discussed, book reviews and synopsis, interviews with authors, etc.
But they also have a blog, which offers a weekly feature called "Like, Try, Why". Each one is sequentially numbered (for example, this week is "Like, Try, Why #21" pictured on the left) and focuses on readalikes for three very popular YA books.
It's simple, it's clean and best of all it does what a lot of readalike tools don't do - it tells you why the book was suggested, helping the potential reader to determine if it's really something they'd like.
Another great thing is, libraries are encouraged to print them off as posters and put them up (most are available in hi-res for that purpose). For free!
View the complete list of Like, Try, Why and keep an eye on the Epicreads.com blog for future posters!