I first found out about Mastodon from my Bass player Mike. Although I kind of ignored his original recommendation so it took a while before I actually let myself get into them.
Now that I have, I wish I hadn't take so long.
"Crack The Skye" was my first experience with them, and since I have moved on to Blood Mountain.
And Leviathan and Remission are still waiting, but why don't you give me a chance to soak in this music for a minute okay?
Mastodon are wicked, and anyone who likes metal should love them.
Noticeable Traits:
Classic Rock Feel
Not growling, but definitely metal vocals
Very unique sound (Must be the way they mix their albums?)
Been nominated for a Grammy of Best Metal Performance
Crusher Destroyer March of the Fire Ants Where Strides the Behemoth Workhorse Ol'e Nessie Burning Man Trainwreck Trampled Under Hoof Trilobite Mother Puncher Elephant Man
The Wolf Is Loose Crystal Skull Sleeping Giant Capillarian Crest Circle of Cysquatch Bladecatcher Colony of Birchmen Hunters of the Sky Hand of Stone This Mortal Soil Siberian Divide Pendulous Skin
My Genre: Metal 
(2002)
(2004)
(2006)
(2009)