Scholastic has a new tool called the Teacher Book Wizard! From the preview, it look very promising. You can search by reading level, genre, and topic. In addition, there is a Book Alike feature to find similar books. What makes this so cool is that you can find similar books on the same grade level, above, or below, using a neat slider tool. (And the Book Wizard suggest books from multiple publishers, not just Scholastic!)
Once you've found books, you can add them to your own book list, and then email or print the list. It looks like it has great promise for helping parents choose books for students--simply put in books that students have enjoyed, and then print out a list of suggestions.
I gave it a whirl to see what it would give me. I like using "Fair Weather" by Richard Peck as a read aloud. It is a little harder than what my students can read on their own, and has delicious details about the late 1800s. One grade level easier than Fair Weather gave me 181 results. Some, like the American Girl book "Changes for Addy", are pretty obvious. But there were results that I would not have come up with on my own, like "Fire in the Hills" by Donna Jo Napoli. There are links that allow you to purchase the books that are offered by Scholastic, and it even tells which books are offered by the book clubs.
I've been frustrated with the weird results that I get with Amazon's search, so this looks like a good new tool to use. Now, if only I had money to actually spend on books...