Well, let's see here:
In two weeks there is the
Heathen Crusade which has already been mentioned.
For just death metal there are the following fests:
Arizona Metal Devastation which is taking place on April 7 & 8 with Haemmorhage, Engorged, Hirax, and more bands to be added.
Maryland Deathfest IV on May 27 & 28 with Haemmorhage, Dismember, Vital Remains, Necrophagist, Pungent Stench, Severe Torture, Skinless, Gorgasm and a bunch more.
Central Illinois Metal Fest on July 21 & 22 with Macabre, Lividity, Lust of Decay, Devourment, Deaden, Immersed In Blood, Rotteness, and more.
Gathering of the Sick on August 4 & 5 with Decrepit Birth, Skinned, Neuraxis, Dead For Days, Devourment, Retch, Insidious Decrepency, and more.
Death metal and some black metal:
Chicago Metal Devastation 2 on April 14 & 15 with Incinerate, Fecal Corpse, Putrid Pile, Prophecy, Ezurate
For doom metal there is:
Templars of Doom on October 13 & 14 with bands TBA.
For just black metal there is:
Gathering of the Bestial Legion bands and time TBA.