I'm a big fan of Adult Swim and of cartoons in general. My kids ages 9,7 and 5 think it's "weird" that I sit and watch "their" shows with them. I just call it good parenting!
Two good cartoons that aren't on adult swim but that I find to be darn good are The Mighty B (Amy Poehler from SNL is writer and voice) and Phineas & Ferb. Both on Nick and worth a look