Another description I hear of them a lot is 'Math-Rock'.
I agree they are very experimental and its always interesting to hear.

How about Behold... The Arctopus?
Anyone?

Sleepytime Gorilla Museum?
Anyone?

Car Bomb?
Anyone?

i like Behold....The Arctopus, but the other two i haven't heard

Maybe I missed 'em, but I'm surprised some of these haven't been mentioned:

Earth - Earth 2
SUNN O))) - White 1/White 2
Khanate - Things Viral
Boris - Absolutego
Gorguts - Obscura
Fleurety - Min Tid Skal Komme

I'd also throw in Orthrelm and The Flying Luttenbachers.

Very good album.

Mr. Bungle is my favorite in this topic though, and one of my favorite bands in general. Disco Volante is an absolute classic.

I find it strange that Mr. Bungle and Meshuggah are being so closely related. I don't know if its just me, but I wouldn't even try to classify Mr. Bungle's sound, much less pigeonhole them into a Metal category. Maybe it was their Metal beginnings with their first few EPs. It just seems like nobody knew what else to make of them. And all a band really needs to do is use unorthodox instruments in relation to their respective genres in order to be termed "Avant-Garde".
...Or maybe I'm just sounding too much like a prick...
But it's like trying to classify Tom Waits.. It's just not gonna happen. Because they (Mr. Bungle) mastered what I like to call "genre-hopping". Metal now, funk next, jazz later, and bring it home with Beach music - hopping from genre to genre, but making it sound good.
That being said, California is easily my favorite album by Bungle. Maybe its because it was their swan song, and I didn't really discover them until after they had broken up, although I did see them when I was 13.
But something else I like about Mr. Bungle is how each of their three LPs stand on their own merits, but sound absolutely nothing alike.

Ephel Duath, anyone?

Yakuza, anyone?