Tanaris is great !

I loved leveling in Tanaris, at 46 or so you can also do ZF runs till 50 or so... Great place, great grinding, some good quests, fun PvP scene if your on a PvP server like myself

Good place, but I guess not everyone loves it as much as myself

So yeah. Ulda, ZF a bit later (may get in earlier then 46 doubt it tho) , Feralas was mentioned that might work (never really went there much myself), I cant really think of to many other places right now.
Are you grinding the water spring fields? Should start there for first few lvls, around 45 I think I went to the area surrounding the caverns of time and kills the dogs, and basilisks and birds there (good skinning and vendor drops as well) Then it was ZF and the cactus valley place till 50 or 51 or something.
Im probably a bit late on this reply but maybe it can help someone else in the future.
-Renth 60 Paladin