Here are some ideas:
Funny: Have you read Roald Dahl's The Twits or George's Marvelous Medicine?
(Younger middle grade)
What about Sideways Stories from Wayside School by Louis Sachar?
(Middle middle grade)
And for a new one for older middle grade kids:
Jasper Dash and the Flame Pitts of Delaware by M.T. Anderson (This is hysterical. Completely silly, but really, really silly. Did you know Delaware has been under the control of an autocratic dictator for years? And it's full of monks and mules?)
For picture books for younger kids, do you know about Phyllis Root? We love, love, love her:
And so far, Calvin and I are enjoying Spchdz, a completely silly book by Jon Sciezcka (Stands for spaceheads) It is a novel with pictures all over the place (this is the new trend. Novels with pictures all over the place, and I will include here our personal favorite that my four-year old up to my ten-year old love, The Ottoline books by Chris Riddell
And one more for teens and adults. I just read this. It is so good. So thought provoking. Not funny at all, but worth it, especially if you enjoy linked short stories (where all the stories deal with the same people, in this case different generations of the same family, but the stories are different.)
Give it a try. And she is one of my favorite authors. And she's Australian, so you can read her books with an accent.
Wolf on the Fold by Judith Clarke
Oh, okay, and Mary has a new favorite book, which I didn't think was that great, but she can't stop reading it and it is very girly, so here it is:
Good for girls in elementary school above second grade, I'd say.