I've played through Fo3 plenty of times but when NV came out it got shelfed, I know its a shame, but part of me wants to rush back to Fo3 and hug my daddy before Project Purity also part of me wants to fully explore the wastes since I never got around to going everywhere that the compas wasn't pointing.
Point is where are good places to visit, assuming I haven't been there.
Where can I find interesting enemies and characters
Who were all of the companions? I only ever found Jericho, Dogmeat and Fawkes
and Any interesting loot I might find on travels to...wherever

:fallout:

The Fallout wiki will tell you all this, though it may spoil things a bit.

Other companions:
RL-3-Caravan outside of Tenpenny Tower
Star Paladin Cross-Citadel
Clover-Paradise Falls
Butch-Rivet City (Muddy Rudder, after completing Trouble on the Homefront)
Sydney (can be a permanent companion if you either don't complete Stealing Independence, or use the awesome Sydney Companion Mod)-National Archives

Some fun places:
The Satellite Dishes in the far Northwest (TONS of raiders)
Evergreen Mills
Fort Bannister

If you're on PC, get Mart's Mutant Mod, turn on increased spawns, and watch the CW turn into a warzone.

If you haven't been to them already, check out:

-The Republic of Dave
-Little Lamplight
-Every building in DC :teehee:

I'd also recommend doing some roleplaying if you want some spice to your next playthrough.
Personally, I think it's always fun to base your character off a real person like John F. Kennedy or Steven Seagal. Or you could create a strange personality for your character. The coolest one I've heard of was from a developer of Fallout 3, who made an account that had the worst combat stats and attacked as little as possible.

Hope you have fun the second time around!