A few comics have been mentioned several times, and deservingly. If I may add my two cents, however, I would add a few more:
Best art in a webcomic: Loading Artist. Despite it being quite new compared to some of the veteran comics out there, it has shot in popularity this past year and not without reason. Not always the funniest, but definitely the most beautiful IMO. http://www.loadingartist.com/
Most relevant (to me in any case): "The Joy of Tech" by GeekCulture.com. Certainly appeals to the tech-orientied masses and is much easier to understand than comics like XKCD. It might not be as intellectually stimulating, but browsing through the archives is a great way to spend some time and have an easy laugh. http://www.geekculture.com/joyoftech/
There you have it.