Here on Tapastic?
There's mine, Captain Ufo. Sci-fi adventure comedy (more like dramedy in the lates pages), 129 episodes so far split in two seasons, some two pages long (due to the site being down sometimes this spring).
The good thing is, if you don't like unfinished comics, each season of my series is a self-contained adventure, so you can read only the first season and have the whole story (although I hope that if you want to give my series a try, you'll stick for season 2, as it a much richer and adventurous story; unless I will be kidnapped by aliens, I swear it's going to continue with it's regular weekly updates untill it's finished).
Among those I follow, there's Runewriters, Patrik the Vampire, City of Blank;
Liar's Dice and Brain Damage are well worth it too and are getting close to 100 episodes.
I'm pretty sure that there are many other good longform comics too.
