I tend to prefer slow-moving webnovels over joke comics, but there are some exceptions.
Subnormality -
http://www.viruscomix.com/subnormality.html
Also a fan here! Goregeous artwork and nice characters. As others have said, updates are sparse, but there's a nice archive of stuff to go through.
Stand Still Stay Silent -
http://www.sssscomic.com/comic.php
Some of the best art I've seen in a webnovel. The environments are highly detailed and atmospheric, and the story engaging! On haitus this month but should start the next chapter soon.
Dresden Codak -
http://dresdencodak.com/
Updates only come one page every one or two months, but are rich with detail. Science fiction, fantasy, philosophy and mystery all rolled up!
He is a Good Boy -
http://hiagb.com/
By the same creator of Gunshow ('this is fine' dog). A very strange story about an anthropomorphic acorn trying to find his way in life. A lot of gore and language, so NSFW, but more complex and expressive than webcomics with a similar "simple" style usually are. Switches between surreal/silly and heart-wrenching with ease, I find.
Go Get a Roomie! -
http://www.gogetaroomie.com/
Okay this is a weird one. It starts off way back as your typical early 2000's pervy webcomic (at least visually), but if you stick with it, quickly evolves into a slice of life with a group of wonderful characters! The art style gets much better, too. And less gratuitous. Still NSFW for (eventually tasteful) nudity and language. One of my absolute favorites! LGBT-friendly!
Headless Bliss -
http://www.headlessbliss.com/
Same creator as GGaR. Hard to describe this one. Dreamlike surreal fantasy with amazing artwork! Something like Moebius, meets Philemon, meets Jodorowsky, meets Go Get a Roomie? Take a gander at this spoiler-free sampling:
http://www.headlessbliss.com/comic/page-9
Mare Internum -
http://www.marecomic.com/
Beautifully drawn sci-fi webnovel about the planet Mars and it's mysteries. Great characters! Slightly NSFW for some language.
Sufficiently Remarkable -
http://sufficientlyremarkable.com/
Slice of life type webcomic with great characters and art. And the absolutely wonderful color palette! Overall, often reminds me of some of Naoki Urasawa's mangas, at least in tone/feeling. Occasional NSFW language.
Johnny Wander stories.
Lucky Penny is a good place to start.
http://www.johnnywander.com/comic/lucky-penny-001
Kind of Bryan Lee O'malley-ish slice-of-life.