Hmm. For the Enclave is a pretty good one, even if the voice acting is kinda garbo. Especially the leader, that is just...bleh. But the story, and missions aren't too bad.
Another good one would be The interhance, which thanks to someguy's brilliant mod making skills, when used with bounties and his esm, it'll have connecting missions, so that's cool.
Hmmm. Boom to the moon is cool. You get to visit the moon in that one.
The new vegas uncut series is pretty cool, it adds a bunch of added quests and the such that were cut.
The new vegas christmas special is pretty good.
Honest hearts reborn, which is a full on total overhaul of the dlc of the mostly same name, and revamps everything and just makes it better.
Milkman is also good.
Hmm. Think that's it.