Packer Backers-Green Bay Packers
Deadheads- Grateful Dead
The Royal Family- Queen
Arnie’s Army-Arnold Palmer
Parrotheads-Jimmy Buffet
Phishheads-Phish
Marty Robbins fans had a nick I think,but cant remember it.Was it Marty’s army?
Adding the word “Nation” to the end of a sports team shouldn’t really count, unless it is “Raider Nation” which is the 1st team that used that…i think.
I don’t know if this is what you’re thinking of, but there’s the “Black Hole” for the Oakland Raiders and the “Dog Pound” for the Cleveland Browns. However, since I’m not a fan of either of these teams, I’m not positive but I think that both of those terms refer to specific seating areas for the respective teams, and not the teams’ fans as a whole.
Arsenal (a British football team) fans are Gooners (derivative of Gunners)
There are numerous other footie related ones, though can think of any off the top of my head.
Oh wait… I forgot possibly the best of all…
Monkey Hangers - Hartlepool United supporters. Long story, google it if you want 
http://en.wikipedia.org/wiki/List_of_English_football_club_nicknames
Ipswich fan here, and I’m particularly pleased to be a Tractor Boy, due to it being a former insult which we turned on its head. It used to be that if we we went ahead, it would be the visiting fans who would be singing ‘one nil, to the tractor boys’. Responding to Liverpool fans with ‘I’d rather be a farmer than a thief’* was a major step to taking it on ourselves.
*Liverpudlians having a thoroughly deserved reputation for light-fingeredness. Or should that say undeserved?
Edit for the Americans among us…those songs are sung to the tunes of ‘Go West’ and ‘She’ll Be Coming Round The Mountain’ 
Packer Backers? Try Cheeseheads.
The Dawg Pound is the east-end bleacher section in Cleveland (both old and new stadiums).
Red Sox: The Fenway Faithful.
David Cook’s fans are calling themselves Cookies. I like it.
Floyd Freaks – The Pink Floyd (at least, in the early 70s).
Sea Divers – Mott the Hoople
Apple Scruffs – Beatle fans after the group broke up; George Harrison wrote a song about them.
There’s also “Red Sox Nation” which, despite its apparent unoriginality, has caught on.
Oakland Raider fans are also referred to with the singular “Raiderfan.”
This fact (or slur depending on you allegiance ) is a basis for a multitude of awesome British football chants, such as the excellent “We’ve got Di Canio, you’ve got our Stereo”.
I suppose, given that Everton fans are equal targets, they all count as both?!
Thereby inspiring the one-upping management in New York to promote the “Yankee Universe”.
Are these the guys that yell, “Up the Arse!”? 
Sick Things – Alice Cooper
Heavy metal band Manowar’s fans are called The Army of the Immortals.
I was gonna give freakalette the opportunity to post this one, but
Juggalos and Juggalettes for fans of the Insane Clown Posse
Hulkamaniacs–fans of Hulk Hogan
Brew Crew–fans of the Milwaukee Brewers
SSG Schwartz
The Apple Scruffs were a gang of girls who used to keep a vigil outside the Apple office and/or EMI Abbey Road; it was before the breakup. In fact, a couple of them were invited in to record backing vocals on “Across the Universe.”
Richard Thompson fans: Dickheads.
Allman Brothers fans are Peachheads.
moe. fans call themselves moe-rons.
One of my friends still has his KISS Army ID.