you can add a lot with just these 3 :
Uncut Wasteland ( stuff and minor npcs that actually were in the game and were patched out for the consoles to handle - essential for any playthrough - not getting it is criminal )
http://www.nexusmods.com/newvegas/mods/56625
Outside Best ( stuff based on dialogue and information existing in the game files but never used in the official game . This might feel a little off at times and has at least one confirmed bug with sherrif meyers, so save many times but do get it because it restores
tons of cool stuff and it's basically what you are asking for )
http://www.nexusmods.com/newvegas/mods/46648/?
Freeside Open ( has quite a bit of cut content , dialogue and ncps . It also includes two other mods from the uncut series , which happen to be the best- most complete in my opinion . It might be the best new vegas mod )
http://www.nexusmods.com/newvegas/mods/46355/?
I would also add the strip open
http://www.nexusmods.com/newvegas/mods/38056/?
Be careful to get comtatible versions with all these ( they do exist in the mods files section )
Beyond those 4 major mods , there are other smaller ones you might wanna add , cool but not that great . Look up the whole uncut series . Also , i'd say grab
Primm Reputation Restored , because small as it might be it feels part of the game
http://www.nexusmods.com/newvegas/mods/48918/?