Yotsuba&! is a manga by Kiyohoko Azuma, the same guy that did Azumanga Daioh.
It's a comedy manga, but not 4 panels like Azumanga was. Instead, it's like a story. It's split into chapters, so they're not always related to each other. It's appropriate for all ages.
Yotsuba is the main character. She's a 5 year old girl who's extremely curious about the world around her, has too much energy, and finds enjoyment in anything. It's really because of her that even the most mundane situations and stuff are made funny. You get chapters about Air conditioners, Swings, Rain, Moving, and stuff like that, yet it's not dull. I really recommend this.
I find it really funny how Azuma uses the phrase "Will you shut up?" often, throughout Azumanga and Yotsuba&!. Just thought I'd say that.
So far there are 5 mangas available in stores. I have the 1st, 4th and 5th so far, I didn't get around to buying the other 2 but I read them a lot at the store anyway.