Way too much blood elf Estrogen in here, and not a single blood elf female has posted...
Also, welcome to Ravenholdt Kumen! You'll find our community might be a little small compared to some but what we lack in numbers we make up for with friendliness and sincerity.
Here's a list of some active Horde-side RP guilds that I've compiled:
<Ashes of Eversong> is an RP guild centered on blood elf culture and politics with an emphasis on sin'dorei/Horde relations. We're a new guild hoping to enrich the community by supporting public events and fostering inter-guild RP. http://us.battle.net/wow/en/forum/topic/7924373746
<Bloodfury Clan> is an all orc, heavy RP guild with a military theme. The guild is "Thrallite," so expect srength, honor, and service to the Horde! They have been a part of Ravenholdt for a long, long time and are strong supports of the community, so any orc RPers are strongly encouraged to check them out! http://us.battle.net/wow/en/forum/topic/7004014911
<Brokentusk Clan> A relatively new heavy troll RP-PvP. As far as I'm aware this is the only guild catering to this theme, so check it out if you're a troll looking for a new place to call home, mon! I'm sure you won't regret it! There isn't a recruitment thread up on the WoW forums yet, but /who in-game should produce some results.
<Coldstar Merchant Co.> RP/PvP/PvE. As the name states, the theme is mercantile and focuses on the acquisition and trade of treasure, artifacts, and weapons. They currently host a public tavern-style event called the "Coldstar Cantina" on a weekly basis that has been running for quite some time now. http://us.battle.net/wow/en/forum/topic/1519283264
<The Jeweled Blood> RP/PvE/PvP. Primarily a blood elf guild that draws inspiration from Elizabethan society and Anne Bishop's The Black Jewels. They don't have a recruitment thread and I'm not sure about who to contact either but /who them in game, I'm sure a member would be glad to answer any questions!
<Hellscreams Eyes> RP-PvP, centered around fanatical support for Garrosh Hellscream. Feeling naughty? You might want to check them out! http://us.battle.net/wow/en/forum/topic/7199404197
<Nightgloom Hollow> A mix of all races, with an emphasis on blood elves and Forsaken unless I am mistaken? I can't seem to find a recruitment post to accurately relay their theme...but the guild is active and I know several members. They are very friendly! /who them to contact a member for more information.
<Order of the Forsaken> As the name implies, they are a heavy RP guild open to all Forsaken and death knights. I can't seem to find a recruitment post for them, either, but I do know they are active and recruiting. I've had the pleasure of meeting several of their members and they are very dedicated and friendly! Contact Garthoneeye in-game for more information.
<Prophets of War> is a "social & leveling family-oriented" guild, that participates in PvP/PvE and RP. I'm not really sure of their theme as it's not provided in their recruitment post, but I'm sure they would be more than happy to answer any questions! http://us.battle.net/wow/en/forum/topic/7006246363
<Silver and Silence> RP/PvP/PvE, with a focus on promoting world PvP. They have a focus on sneaky rogue-ish dealings, from what I've been told. The members are very friendly and would be more than happy to answer any questions! Additionaly, Silver and Silence has been hosting a weekly tavern event in Ratchet at the Broken Keel! Cheers for public RP events! http://us.battle.net/wow/en/forum/topic/7885048552
<Shadowclan> RP Heavy, PvP Medium, PvE Medium. Orcs and trolls only. Couldn't find a recruitment thread but contact Ruptup for more information. www.shadowclan.org.
<Unyielding Force of Lore> RP/PvP/PvE, with a general pro-Horde theme that stands in direct opposition to any that would seek to divide it. Advertise a social environment and seem like a really laid back group! http://us.battle.net/wow/en/forum/topic/7811652385#4