Eddie Fitzgerald points us to this big post on Al Capp and Li'l Abner at the ASIFA-Hollywood Archive.
I don't think Capp is as well-known today as Walt Kelly, but, much as I love Pogo, I think in some ways I like Li'l Abner even better, and its best stories are about the best I've ever seen in comic strips. Capp's attitude to his characters was much less good-natured than Kelly's; he has contempt for most of his characters and most contempt of all for his "hero," Li'l Abner. But that gives a kind of complexity to the strip, because his open contempt for Abner butts against the moments of goodness and likability that he gives to Abner and other characters.
Update: In comments, Thad K points out that Mark Kausler has been posting strips from Capp's "Joanie Phoanie" story from the late '60s, the ultimate symbol of his decline into unfunniness. Too much is sometimes made of Capp's move to the political right; I don't think that specifically is what caused him to stop being funny. (My Dad recalls Capp going on talk shows and saying similar things in the '50s, when the strip was still funny.) Capp hated everybody and his sense of humor was very dark, very bitter. At some point the sense of humor started to fade away and all that was left was the bitterness; the problem with the Joanie Phoanie strip is not that he's angry at her or at student protests, but that there isn't much humor here. Plus he caricatures Baez, a good-looking woman, as an ugly crone: if Al Capp passes up an opportunity to draw a good-looking woman, you know he's letting his anger overwhelm his sense of humor and his love of drawing women.