The one i have let's you do a lot more then just return to the waste, here is the authors readme from the mod.
Mod: Freeplay after Main Quest
Author: Khet
Permissions: None. Don't modify or redistribute this mod in part or whole.
Download: http://www.newvegasnexus.com/downloads/file.php?id=35450
============
Introduction
============
FPMQ allows not only continued play after completing the Hoover Dam Battle, but also grants the player three choice on how to continue. With this option, the Hoover Dam Battle 'never happened'
Choice One: No Change
This will not make any changes to the game. Any faction gain/loss that happened during the Battle will remain.
Choice Two: Reset
This will reset faction standings for Great Khans, Brotherhood of Steel, NCR, Caesar's Legion and Powder Gangers back to their pre-battle settings. With this option, the Hoover Dam Battle 'never happened'
Choice Three: Continue
This is the biggest part of the mod. It will change existing NPCs based on who you helped (House, NCR, Legion or Indy), change territory occupancy, add new NPCs in certain locations, unlock a plethora of quests for you entertainment (or for you to ignore), and more. Essentially, this option will continue the game as if the Hoover Dam Battle actually happened, with your choices affecting the Mojave both instantly, and throughout the quests. Please note that if you destroyed the Legion, all quests tied to that faction will fail. The same goes for defeating the NCR, or both if you went Indy.
============
Installation
============
Place the .esp and any Meshes and/or Texture folders in the following directory:
Steam\steamapps\common\fallout new vegas\Data
Launch the Fallout New Vegas launcher, click on Data Files and check Freeplay after Main Quest.
Enjoy.
If you pirated Fallout New Vegas I won't help you.
==================
Upcomming Features
==================
A lot. This is just a quick rundown of what to expect in the future.
-Remove/Add NPCs in the game world depending on who the player helped during the Hoover Dam Battle
-Add Rebuild Quests
+Rebuild Quests will be faction specific.
+With Legion/NCR they will deal with rooting out the remaining enemy forces, recovering/claiming territory, rebuilding locations, etc
+With Indy they will deal with rooting out the remaining enemy forces, recovering/claim territory, rebuilding locations, running New Vegas, hiring people to help run New Vegas, etc.
-Plus More. I'll add them to the File Description on the Nexus as I remember/think of them.
==========
Known Bugs
==========
Just one. If the game crashes shortly after the beginning of the ending movie, simply disable the mod, load up a saved game, complete the quest and save the game again at any point about 30 seconds after the movie has started. Re-enable the mod, load up the movie saved game, and enjoy. I'm still looking into what causes this, but at least it's easy to get around for the time being.
==============================================================================
Version History (Or as I like to call it, the thing I always forget to update)
==============================================================================
1.0 - Release. Nothing fancy, no choices, just keep playing.
1.01 - Now we're talking. Adds the post-ending menu, No Change and Reset options working.