It's only November, but the lists of Best Books of 2009 have already starting coming out! Some interesting ones:
Publisher's Weekly Best Children's Books of 2009
(includes pictures books as well as fiction and nonfiction for older readers)
Amazon.com's Top 10 Picture Books of 2009
Amazon.com's Top 10 Books of 2009 of Middle-Grade Readers
Amazon.com's Top 10 Teen/YA Books of 2009
Lots of good holiday gift suggestions here! I'll save my own personal Best of 2009 list until the end of the year.