• Just the Right Size, Extreme Animals (and others) by Nicola Davies
• How to Get Organized Without Losing It by Janet S. Fox
• How To Do Homework Without Throwing Up by Trevor Romain
• Manners Mash-Up: A Goofy Guide to Good Behavior by Tedd Arnold and others
• What To Do About Alice by Barbara Kerley
• The Basher books (Physics, Periodic Table, Biology, etc.) by Simon Basher
• Kathleen Krull’s Lives of the… series 
• You Wouldn’t Have Wanted To Be A… series by various authors
• Fingers, Forks, & Chopsticks by Patricia Lauber 
• Poop Happened by Sarah Albee
• Americapedia by Jodi Lynn Anderson, Daniel Ehrenhaft, Andisheh Nouraee 
• How They Croaked by Georgia Bragg 
• Bugs and Bugsicles: Insects in the Winter by Amy Hansen
• What to Expect When You’re Expecting… series by Bridget Heos
• It’s Spit-acular: The Secrets of Saliva by Melissa Stewart 
• The Truth About Poop by Susan E. Goodman
• Gee Whiz by Susan E. Goodman
• See How They Run by Susan E. Goodman
• Fartiste by Kathleen Krull (which I blogged about here)
• Do Pigs Have Stripes? by Melanie Walsh
• Bubble Homes and Fish Farts by Fiona Bayrock
• Ant, Ant, Ant, An Insect Chant by April Pulley Sayre
• What’s So Funny? Making Sense of Humor by Donna M. Jackson

This is just a sampling of our favorites. Do you have any to add? Please let us know in the comments!
I found it interesting that often the humor is primarily in the illustrations, with the text playing it fairly straight. In fact, in many cases it’s only the juxtaposition of the two that tickles your funny bone. In others, the humor is mild (a smile rather than a belly laugh) or is just hinted at rather than being an explicit joke. Sometimes, the topic itself is pretty funny, but the text is fairly serious. Given how much kids love to read humor, I wonder if that’s all just coincidence, or if humor just isn’t as tolerated in nonfiction texts, or maybe nonfiction writers just don’t have a sense of humor (I’m sure not buying that last one!). Thoughts?