check out
http://www.drmcninja.com. Dr. McNinja is a doctor who is also a ninja. it's one of the funniest things i've ever read. don't start with the last page, everything is in stories. go to the archive and read the first or second story first.
i second Questionable Content.
as for physical comics, Jhonen Vasquez would be my recommendation. "Johnny the Homicidal Maniac" is disgusting, slightly disturbing and hilarious.
also, if you can find them, comics by a guy named Jeff LeVine are great. i'm not sure if he's still working, i've only got one book of his, "The Days Go By Like Broken Records."
plus X-Men. gotta love the X-Men.