This is a great place to look up any title and receive a quick synopsis, as well as actual reader responses to any book. You can create an account, but only if you want to create your own booklists or reviews.
Project Gutenberg is a great place to look for classics that have passed into the public domain, with a Top 100 e-books list every day. These books are free and available for download to a variety of devices.
Find reviews of the newest YA literature and check out the Reading Rants Lists on the left for lists collected by audience and type.
YALSA's Book Awards and Booklists are tailored specifically for the young adult reader. Use these awards and lists as a guide for all your YA choices.
The KDL "What's Next"(TM) Books in Series Database let's you know what's next and what's new with your favorite authors and series.
This site gives you suggestions for books based on titles you give for what you would like to read. You can even build your own "book lists" to keep track of titles to read later.