First semester & Second semester Spanish love songs
Side-splitting funny.

Young Chang Heavy Industries
This is more art than humor (though some of it's pretty funny). It's text-based Flash movies set to music. Very creative, wish I'd thought of it.

Spamusement
Cartoons based on actual spam subject lines.

Flying Spaghetti Monster
Suggests that if schools are teaching the "Intelligent Design" theory of creation alongside evolution, they should also teach the "Flying Spaghetti Monster" theory.

Las Vegas on $19 a day
This is a long article, but it's the funniest thing I've ever read on the net (and that's saying a lot).

Postmodernism Generator
Generates a brand-new mess of academic gobbledygook each time you click. The randomly-constructed senences are grammatically perfect, and impossible to understand.

Americans for Purity
A faux anti-masturbation organization. The really funny part is their hate mail page, with all the readers who don't get that it's a joke.

Amy's Alphabet of Grievences
Amy shares her unique (and rather amusing) take on life, letter by letter.

AntiMagnet.com
Humorous criticism about those magnets people put on cars.

Strange Signs
A collection of photographs of real (yet improbable) store, highway, and other signs, such as, "Don't let worries kill you. Let the church help."

Horse Hate
An advice column authored by a horse.

Beat Jeremy Coon
My friend Rhys Southan's blog, where he documents his attempts to out-do his high school classmate Jeremy Coon (producer of "Napolean Dynamite") before their 10-year high school reunion.

Why English is hard to learn
Very interesting examples.

Children's art critic
Condemning kids' drawings mercilessly

The Onion
A professionally-produced newspaper made to look like the real thing, except it's not. They also have an online version. These guys set the standard for humor on the net.