We recently launched the Guild Mentoring Program ( http://eu.battle.net/wow/en/blog/5423616#blog ), and our mentors are eagerly awaiting new faces to welcome and show around.
For more information on the respective guilds, please visit their introduction threads (linked below). These may help you decide which realm and faction you might want to join.
Enigma, Alliance - http://eu.battle.net/wow/en/forum/topic/5208453243
Warseeker Tribe, Horde - http://eu.battle.net/wow/en/forum/topic/5208453153
Broken Faith, Horde - http://eu.battle.net/wow/en/forum/topic/5327282859#1
Mea Culpa, Alliance - http://eu.battle.net/wow/en/forum/topic/5207773060
Vice Versa, Alliance - http://eu.battle.net/wow/en/forum/topic/5207843609
Chaotic Good, Alliance - http://eu.battle.net/wow/en/forum/topic/5208455440
Wombles Of The World, Horde - http://eu.battle.net/wow/en/forum/topic/5207753921
Order of Gray, Alliance - http://eu.battle.net/wow/en/forum/topic/5208755941
The One, Alliance - http://eu.battle.net/wow/en/forum/topic/5208754984
Please note that, for the duration of the program, all guilds have been renamed to either Blizzard Mentor Horde or Blizzard Mentor Alliance to make them easier for you to identify.