Those actually aren’t as bad as I was expecting, though I’ve only ever heard about Book of Biff before and it’s really not my thing.
My personal favorites are:
Order of the Stick (and Erfworld is good too)
Tales of the Questor (along with about 5 other series that are all pretty decent)
Sinfest (not exactly what it sounds like, but good)
Girl Genius (Drawn by masterful Phil Foglio, who also does Phil & Dixie along with the now finished Buck Godot)
Schlock Mercenary (starts off with horrible art, but eventually characters, writing and artwork improves exponentially with 10 years worth of archives to run through)
Sluggy Freelance (starts off downright horribly, but much like Schlock Mercenary manages to improve their characters, writing, and art. Just like Schlock, there are 10 years of daily updates to cover)
Questionable Content(Lots of indie band references, but never in a way that you actually need to know anything about them to be able to get a chuckle out of the conversations that take place)
Weregeek(Geek hobby references of all kinds across the spectrum)
Errant Story (not as good as Girl Genius, but still pretty good)
Nodwick (another series that, like Phil & Dixie, started out in Dragon Magazine)
Dr. McNinja (the name should say it all, epic ideas area constant theme and somehow are written so that you totally accept them as believable)
NerfNow (primarily focuses on TF2 related subject, but occasionally branches out to other games)
Brawl in the Family (similar to NerfNow, but focusing on the various Characters from Super Smash Bros Brawl.
I’m not even going to bother mentioning Penny Arcade, XKCD, or Roosterteeth, someone else can tell you about those.