Unofficial Colour Combination Deck Terminologies

Two Colour

RtR Block:
White/Blue: Azorius
Blue/Red: Izzet
White/Green: Selesnya
Black/Green: Golgari
Red/Black: Rakdos

GtC Block:
White/Black: Orzhov
White/Red: Boros
Green/Red: Gruul
Blue/Green: Simic
Blue/Black: Dimir

Three Colour Official Names from Shards
White/Blue/Black: Esper http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=137913
White/Red/Green: Naya http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=376423
Green/Red/Black: Jund http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=376383
Blue/Red/Black: Grixis http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=376357
White/Blue/Green: Bant http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=137931

Three Colour Unofficial Names popularized by MtG communities
White/Green/Black: Junk http://magic.tcgplayer.com/db/deck.asp?deck_id=1055670
White/Blue/Red: American http://tappedout.net/mtg-decks/american-control-retired/
White/Red/Black: Daiga
Red/Blue/Green: RUG
Black/Blue/Green: BUG

Another posting on names can be found here: http://boardgames.stackexchange.com/questions/11550/what-are-the-names-for-magics-different-colour-combinations