I believe Horde has a fair bit more activity than Alliance these days, although it’s mostly within the guilds on both factions. Walk-up RP is pretty much dead, unless you happen to stumble upon one of the guilds gathering at a tavern somewhere.
Convocation of Elrendar and Wayward Vagrants have been cooperating a fair bit lately and are doing regular social RP both on their own and with each other.
The Coven are up and about somewhere and the same goes for The Beastmaw Warband, although I believe both of these mostly keep to themselves.