The page here called "Best Children's Books of 2009: The Big List of Lists" keeps growing. I'm waiting on School Library Journal's lineup*, which ought to be announced shortly; meanwhile, I've added a bunch of links recently, including the following:
Amelia Bloomer Project nominations. "Recommended feminist literature" for children.
Best Hockey Books for Kids, at Joe Pelletier's Greatest Hockey Legends.com
Boing Boing Gift Guide 2009: Kids. Some 2009 books, some older.
Canadian Children's Literature Awards: TD Canadian Children's Literature Award, Marilyn Baillie Picture Book Award, Nora Fleck Award for Canadian Children's Nonfiction, and Geoffrey Bilson Award for Historical Fiction for Young People.
The Independent: The 50 Best Winter Reads (UK). Mostly adult titles, but some books for children.
Tablet Magazine: Best Jewish picture books
Also: be sure to look at Largehearted Boy's "2009 Year-End Online Music Lists" and "Online 'Best of 2009' Book Lists," as well as MotherReader's updated "105 Ways to Give a Book," in which MR pairs books with toys or other gifts.
*Update: Here's School Library Journal's list.