Old Nuclear Test Site to the Southeast is fun. Lots of ghouls to shoot, hardened robots, a crashed verti-bird nearby and the animal husbandery farm nearby is perfect for harvesting brahmin and bighorner meat for recipes.
It's also near an interesting airfield that is occupied by some radscorpions. If someone ever makes a pilotable vert-bird mod for new vegas, that airfield would be a great place to pick it up, park it. maintain it. It's south of camp searchlight.
I like to go hunting up and around Mount Charleston, plenty of big-horners and other wildlife. Plus theres a pretty good view of New Vegas and the surrounding area...
Vault 11 was probably the most interesting place I've ever been to in my entire expierence with the game, despite the fact that I've only been to it once in maybe 40 diferent save files. I would definately not reccomend going there at a low level, but if you are, bring