Adventurers! has finished its run, but is still fun to read. Also, there you can follow the link to Webrunner/Mark Shallow's newer comic, Antihero for Hire.
The Adventures of Dr. McNinja is silly but funny.
AppleGeeks sorta qualifies as sci-fi......but is mostly just humor.
Chisuji is a sort of fantasy/sci-fi webcomic, but slow-updating. A few pages of flashback to the nigh-immortal redheaded demonhunter's past are probably NSFW. Most pages are in color, but occasionally they have B&W pages when the colorist is too busy.
Dominic Deegan: Oracle for Hire is a fantasy webcomic that updates frequently. Most pages are black and white, with color for one or two pages per week (Mookie updates 3-5 times a week). Occasionally Not Safe For Work. More of a comedy and romance saga than anything else, but it IS funny and has an interesting story.
Dresden Codak is wierd, but sci-fi and a bit of fantasy. Funny, but confusing sometimes; a lot of philosophical and erudite things in it.
Eidolic Fringe is old and sadly no longer updating, as the creators apparently had to abandon the project for some reason. Still, it's an interesting fantasy webcomic, albeit abruptly left off in the middle of things.
AesirCorp is a sort of fantasy webcomic, but hasn't run very far before going on hiatus. Dunno if the writer/artist will be getting back to that project or not.
Freelance Explorer Indavo is a sci-fi webcomic. A few pages may be NSFW.
I have no idea if or when Bluebug will resume updating
Kurenai Mashin, but I assume it'll be another year or two before she resumes the webcomic. A fantasy webcomic about a blind elven assassin (no kidding) known as Kurenai Mashin, the Crimson Devil.
Mystic Revolution is a comic about a fictional online VR game of the future; the game is a fantasy setting sort of like .hack//sign or an MMORPG, so it's essentially a fantasy webcomic.
No Need For Bushido! is a sort of quasi-historical feudal-Japan webcomic. More humor than story, but still.
Seraphic Blue is sort of a sci-fi webcomic, but slow-updating. Not sure when Nami and Rika will resume updating.
Skyfall Online Manga is a fantasy webcomic about elves, dangerous magic, and evil plots. Might be one or two NSFW pages in there, or not, I forget.
Sodium Eyes is just funny. It's not sci-fi or fantasy, but it's amusing. Relatively new. Geeky and kind of random.
The Fortuna Saga is a sprite comic based on, I think, Final Fantasy IV or thereabouts, I forget, since I never played the first few FF games. Very story-oriented, not so much humor. Fortuna Saga is having technical difficulties at the moment, but will probably be back online in a few days or a week.
The Seraph Inn is the hub for a few webmanga by the same author/artist. Start with Inverloch, the first of them. The Phoenix Requiem is newer, and Inverloch has finished its story. Not so much humor in these either, they're story-focused. Haven't read Dreamless yet so I dunno what that's up with that one.
Wayfarer's Moon is a fantasy webcomic. Relatively new, barely a few chapters done. Story-focused. Read the writer's blogs/articles too; that's where the humor lies.
White Noise is a near-future sci-fi webcomic. Aliens have landed and effed up the Earth, then gone away after mankind sort of fought them off. Now folks live in sealed-off cities to avoid the toxic clouds left behind by the alien terraforming attempt (Earth's atmosphere wasn't quite suited to them). One kid with a mutation from one of the abandoned alien bio-research labs tries to get by and escape those who'd kill or experiment on him just because he's got a
tail. And he has wierd dreams in which one of the aliens talks to him, sort of, though it rarely makes sense (it's a freaking alien, after all). No one knows if the aliens are coming back and really really hope they don't, because humanity had a hard enough time trying to resist them the first time. Kind of slow updating, but at least it's still going.
Zap! In Space is a sci-fi webcomic. Funny and it's got a story. With psychics! Zap himself is an amnesiac telepath/telekinetic.
The War of Winds, a fantasy webcomic.
Fox Tails, another fantasy webcomic, about kitsune (magical shapechanging fox-folk) harassing and mooching off of a random guy in the modern world..... And the occasional interference of demons and celestial beings. More about humor than story, but it's definitely got a plotline and stuff.
And I don't have a direct link to DandDorks, but it's a funny webcomic about a D&D group. I usually just go to BuzzComics and find DandDorks somewhere on the first or second page of its Top 100 list.