If you're a teacher or librarian (or both, of course!), you definitely want an account with NetGalley!
A service for "people who read and recommend books," NetGalley allows users to download and read galleys of upcoming books. It's browsable by genre or publisher, and you can search by author, title, publisher, imprint or genre.
It works with multiple devices--Kindle, Nook, and iPad, to name the big three--and the site provides good instructions for loading them onto your specific device.
How It Works:
Very easy! Once you find a book you want, just hit the request option. Your request is sent to the publisher, usually with a reply in a few days. If you have one, be sure to add your ALA number to your profile. Publishers are more likely to grant your request if they know you have purchasing power!
You'll have most galleys for 60 days, plenty of time to read!
(Thanks for the head's up, Shannon Mersand!)
UPDATE: NetGalley also offers librarian-specific newsletter, NetGalley at the Library, which highlights upcoming notable books, among other things.