Lewis Trondheim's diary comics are so good I'm actually posting a puke joke here.
My first exposure to Lewis Trondheim was Mister O, which is one of the funniest things I've ever read--the first time I looked at it, there were at least two or three pages that made me laugh so hard I was lying on the floor gasping--and I've been skimming bits of his enormous catalogue ever since, trying to find something I like as much. (The sequel Mister I wasn't anywhere near as good, and I'm sort of mystified by A.L.I.E.E.E.N.) Most of his hundred-plus books aren't available in English; if you're reading this and you know which of his books are worth seeking out in French, feel free to recommend some stuff in the comments.
Little Nothings is 120 pages' worth of his diary comics, which he posts every few days at his blog, and they're some of the best diary comics I've seen. They don't have the same kind of broad humor as other books of his, but they're perceptive, totally charming, and exquisitely drawn--he draws himself as some kind of bird (and everyone else as animals too, which means that every drawing of a character is a little sight gag). His artwork here is deceptively simple--pen-and-ink line drawings, shaded with watercolors--but the coloring gives a great sense of lighting, and usually underscores the jokes, too. Look at the puke joke again: the splotches of yellow capture the effect of late-night streetlights, direct the eye toward Trondheim and his friends, and quietly recapitulate the gag while they're at it.
What I think I like best about it is Trondheim's attitude toward himself, which is always tricky to negotiate when you're drawing your own immediate experiences and then showing them to the world. He's amused by himself, but not particularly self-important; he's sometimes the butt of his jokes, but there's never really a sense of self-loathing. The root of his humor is his awareness of how his own mind works. It's funny when he sits on a train, watching people run for it, and then bursts into a sweat, wondering "And me? Am I on the train? Did I make it on time?" But it's even funnier when he realizes that he asks himself the same question every time.
A good-sized chunk of the book can be read here, in reverse order, which may make some of Trondheim's running gags confusing. If you can read French (or just like his drawings), his current blog entries are here, and use the weirdest and funniest system for dealing with old entries I've ever encountered. It's definitely low-key--if you want ambition from Trondheim, there's the Dungeon series, which I've yet to read most of--but it's Excellent.