Nothing by Down, Mastodon, or Baroness. I'm already familiar with them.

Thank you in advance.

Boris and Isis are the first two bands that come to mind, although some of the albums I wouldn't really consider sludge.

Thank you very much. Which albums of theirs would you consider sludge?

Hm, I think Pink or Smile would work for Boris. Isis, to be honest, I'm not too familiar with. I just know that people say they're sludge.

I never considered Down or Mastodon sludge, but hey, what do I know?
I'd suggest Sourvein. The only release I'm real familiar with is Ghetto Angel, which I like immensely. Sludge that's catchy, fun, and heavy as hell.
http://www.youtube.com/watch?v=Fxx3dEJBfIk
If you like Sourvein, you might like Electric Wizard as well.
I don't know if you just want to start out with regular sludge, but if you'd like something a little different, check out Birushanah. Awesome sludge metal with traditional Japanese music influence. Generation of Vipers isn't bad, either; I guess they're described as Sludge/Post-Hardcore.

I don't really consider Mastodon sludge either, but some people think they are and I didn't want recs of them. However, I could swear that Down is sludge....

But thanks for the recs. I'll watch the video when I have access to a non-dial up connection.

Down have nothing to do with Sludge musically. The members all play in other bands that are part of the NOLA Sludge scene, but Down itself isn't a Sludge band in the slightest.

For a solid grounding in what the genre is all about, you should look into Crowbar, Soilent Green and Eyehategod.

Eyehategod.
Grief.
Corrupted.

Pretty much all you need.

While we're on the subject, what genre is Down exactly? I'm not doubting you or anything, I just want to be correct for future reference.

Been thinking about trying Crowbar for awhile now...

I'd call it "kinda groovy sludgey stuff," but good thing we're on the encyclopaedia metallum, which informs me they are just good ole southern metal.

My rec: Capricorns. Their style is pretty diverse so you're bound to find at least a song or two you'll like from them.

Yeah I saw the "southern metal" thing and I just kinda raised an eyebrow.

I second Eyehategod.

I third Eyehategod

Crowbar
Iron Monkey
High on Fire

High On Fire aren't really sludge. More of a stoner/heavy metal/thrash hybrid, or something.

For sludge, I definitely recommend listening to Black Flag's My War, especially the second half. Probably the first real sludge. From there you should check out some early Melvins as well. The NOLA stuff should be next on your list.