I'm not all that into the slice of life genre either, but I've seen Azumanga Daioh at cons (and I agree - Yotsuba is much better). And a friend showed me Lucky Star

I've heard Lucky Star dissed as "cute girls for nerd boys to watch" but, honestly, as a pretty damn nerdy girl I really recognized myself in their little discussions about nothing. It's also not as overtly sexualised as many for-über-nerds animes, so I enjoyed it. But it's veeery mellow, not a good series to marathon