How have I not written about these guys yet? They are AWESOME.
According to their website: "Sterling’s children’s list includes picture books and non-fiction. We do not publish fictional chapter books or novels. Our non-fiction list primarily focuses on activity-based subjects, such as: crafts, activities, puzzles (math/word/picture/logic), and science experiments. We also have a small focus on history and biographies."
Other things that are (not quite as) awesome: http://1000awesomethings.com