Don't forget about the 2 whole quests in Azshara
I actually started hitting the higher areas at 49 (after quite a stay in tanaris- there are quests at the dock too, if you haven't gotten those yet), but now am having the same problem where I don't seem to have any more quests available to me. It seems like I've done everything in Un'goro, felwood, at least half of searing gorge, all the lame grinding quests in the blasted lands, so on and so forth, and yet I'm still only 51.
Any suggestions for the low 50s while we're at it?