The Mansion of ERating: G
Art: B
Updates: Daily
I figured I'd start with my favorite comic,
The Mansion of E by Robert Cook. The art is relatively primitive, but I don't think it matters much. This story takes place in an unbelievably huge mansion--actually, in its "basement" and the surrounding woods, for the most part. "The Basement" is a huge subterranean world, where dwell any number of peculiar, sentient creatures.
The plot is hilarious, as well as very intricate; the comic's been going for over 5 years, and less than 48 hours have elapsed in-story. I guess a lot of activity is to be expected on "The Day That Changes Everything." The scalpsuckers and fleebs are incredibly cute.

I'm not going to try to summarize everything that's going on. Suffice it to say that it's very interesting and complex.
Complete and careful reading of the archives is absolutely mandatory if you want to understand what's going on. There are a huge number of characters to remember. Thankfully, when somebody appears who hasn't been seen for a while, a link is posted to help us remember.
In short, this comic should be an enjoyable read to just about anybody who's able to commit the time.