I'm not sure if this fits the general criteria, but I'll post it anyway! I'm sure that, if you frequent the internets and enjoy comics, you must've seen some of these before, but one the off-chance that you haven't!

My favourites are;

8-Bit Theatre - http://www.nuklearpower.com
- The king of sprite comics, 1150+ pages long. Best summed up by one of its characters; "Wait! That is not how we do things around here, buddy. ...First we have to argue incessantly over semantics. Then one of us has to hurt one or all of us."
Overcompensating - http://www.overcompensating.com
- "The true story of a cartoon boy who thinks he is a like a cowboy poet who runs the world's largest webcomics distribution company."
White Ninja - http://www.whiteninjacomics.com/
- I shall quote the author: "White Ninja Comics are not for the weak of mind. They are a brilliant satirical commentary on controversial worldly issues. They can be enjoyed on many levels. Scholars, Philosophers, and the like, who possess the intellect to analyze and break down the comics to their hidden, and often devious, roots, will enjoy White Ninja to its fullest degree. Others, like you and I, however, can still enjoy the comics for their light-hearted surface humour and funny drawings.'"
Dr. McNinja - http://drmcninja.com/index.html
- He's a doctor AND a ninja! One hand heals while the other kills! Trust him, he IS a doctor and he knows SCIENCE! Far too well drawn to be free, but it is anyway!
VG Cats - http://www.vgcats.com/
- A video game comic. It deals with jokes concerning video games. Used ot be updated quite frequently, but now is almost dead. Sad, but who can blame him?
Dresden Codak - http://dresdencodak.com/2007/02/08/pom/
- Full of amazing drawings! Philosopical jokes and a extravagant transhumanist storyline! See the afterlife reserved exclusively for those who don't believe in it! And it has time travel! Eeverybody loves time travel!
Muertitos - http://muertitos.comicgenesis.com/
- "A comedy about dead kids."
The Nonadventures of Wonderella - http://nonadventures.com/
- Some bad things happened and her planet was destroyed. She was sent to earth where she developed fantastic powers! But those were lame, so the vaguely greco-romanic godhead gave her new ones instead! She can not fly, but she can TOTALLY jump hella high! Her neverending battle is to protect the people of earth! And by earth we mean the united states exclusively, especially new york.

I tried to pretty it up a little. There are probably others, but I can't recall them right now.

uhu?

Pain to read on the computer? I know how you feel buddy. Try investing in a cheap monochrome laser printer - you won't regret it.

if you know anything about DnD then you will love order of the stick

My favourite webcomics are xkcd http://xkcd.com/183/, I especially like the mouseovers and sinfest http://www.sinfest.net/archive_page.php?comicID=2679 ^^

Aside from some that were already posted, I like:

http://www.pbfcomics.com/ Unfortunately discontinued. http://truckbearingkibble.com/ is similar but not as good, and on hiatus too.
http://www.smbc-comics.com/ also makes me laugh at times, although many of its comics are a bit too similar.
http://nedroid.com/ also has it moments.

http://googumproduce.com/trollgame
Trevor Downs is not a murderer but he killed a girl. Trevor is mysteriously invited to a competition where the contestants must troll the general public for points. The one with the most points after a one month period wins $10 million.

I forgot about pbfcomics. I like that one quite a lot too. ^^. The other comics seems pretty funny too

Nedroid ALWAYS has it's moments.

also, Homestuck from http://www.mspaintadventures.com/ will have you hooked for a long time. Even more impressive is that it really is all done in MS paint.

the other few I read are

http://tailscomic.com/

about a guy who aspires to be a comic artist/writer while taking care of a crapload of cats while constantly dealing with the ups and downs (moreso downs) of his life.

effort comics! http://thechipperwhale.com/

about some comic where humans and cartoons co-exist in the real world. Kinda NWS

http://www.octopuspie.com/

about two women who live in Brooklyn, NY who come from totally different social circles and how they deal with one another

http://www.gunshowcomic.com

extremely funny, by a really nice guy named KC Green

I love the Order of Stick as well! I don't know much about D&D, but I don't think it makes a difference, because it is still funny. http://www.giantitp.com/comics/ootslatest.html

Questionable Content is about some 20 or so year old people, dealing with dating and just social issues. There are two characters, Hannelore and Marigold who have to deal with social issues, which I think people on this board might like them. http://questionablecontent.net

Sam and Fuzzy is about a man and a talking bear. Something about it is awesome when things hit the fan each week. http://www.samandfuzzy.com

Shortpacked is for those who love the whole toy/action figure, everyday humour drudgery that is work and batman. http://www.shortpacked.com

Hope you enjoy them.

Penny Arcade
Dark Bolt
Cyanide and Happiness

Damn you Sauske and posting questional content before I do :P

Questionable Content is one of my favourites too. I also read Gunnerkrigg Court and The Phoenix Requiem.

I hate to admit I read girly romance comics like Red String and The Way to Your Heart. If someone knows other webcomics like these, please tell me.

I love White Ninja! I also like http://www.phdcomics.com and http://www.skinnypanda.com

Skinny Panda is no longer updated though

I thought this one (someone introduced me to it recently) is pretty funny at times:

http://oglaf.com

Boxer Hockey http://boxerhockey.fireball20xl.com

;~; Remembering the awful things that happen later, I still love this comic.

HOMESTUCK