I read a bunch of webcomics, but the ones I seriously care about are Girl Genius, Order of the Stick, and Gunnerkrigg Court.
As for print comics:
Amazing Spider-Man
Ultimate Spider-Man[footnote]I wasn't a fan of what they did to Peter Parker, but I admit the new guy is growing on me as a character[/footnote]
The DC comics I read are all in the new 52 continuity
Teen Titans
Superboy (given how closely it's tied to Teen Titans, you kind of have to do both)
Supergirl
Detective Comics
Justice League
Manga:
One Piece
Black Lagoon - which is finally coming off of hiatus after two years!
Rurouni kenshin - I tend to reread this once a year, due to awesomeness.