On Aggramar did you try the addon from Horde side or Aliiance? I've seen quite a few people on horde over there. Not sure about Alliance.
My server, Twisting Nether, is a good place for Alliance. We got about 10-12 other people F2P's here on Alliance and i've seen quite a few Horde here too. We queue for bg's together here sometimes and occasionally play arenas. Unfortunately, I'm the only one who uses the F2P addon on alliance side. I'm trying to get the others here to use it. You can usually find them at Goldshire and its still loads of fun. I've also seen a lot of Alliance F2P's from Spinebreaker. They also mentioned that they occasionally play arena games. I've heard Burning Steppes is also a good server.
Try rolling an Alliance on Twisting Nether. It'd be great to have more people to hang out with! : )