EDIT: Arg, submitted too soon. Oh well, read on!

This mod adds two "new" companions to the game... (well, new-ish) being Dean Domino from Dead Money and Follows-Chalk from Honest Hearts.
Because I'm lazy, I'm using the http://www.newvegasnexus.com/downloads/file.php?id=38059 , and these companions are also FULLY VOICED! Well, it's not that amazing, since I'm using the voice/lip-sync files from their respective DLCs. But it's still pretty cool!

How it works:

After each DLC, and if these companions are alive and (in Chalk's case) , then the player will recieve two new quests, both following in Obsidian's tradition of using song titles/lyrics for the names for that added immersion factor.

Dean's Quest is titled "http://www.youtube.com/watch?v=crFQpOCDfEc", and involves the player stumbling across a pile of dead Jackals and equally dead mercenaries (on their way to Vegas to, naturally, rob the Strip Ocean's 11-style). The only survivor of this battle, is naturally Dean Domino, who has been shot. The player has to cure him (with a Doctor's Bag or a Medicine check), and will then be able to recruit him.

Chalk's Quest is titled "http://www.youtube.com/watch?v=bCY09s-c41A", and involves the player finding a small encampment of slavers, who have, of course, captured Follows-Chalk and are intending to sell him to the Legion. The player can choose to either buy his freedom, buy him as a slave or can kill the slavers and rescue him.

Additionally, each companion has all-new perks! (you only get one of Chalk's, depending on how you recruit him)

Ghoulish Anatomy: "Removing that bullet from Dean has made you... intimately familiar with the anatomy of ghouls. While Dean Domino is a companion, you'll do an additional 5 points of damage to all ghouls, feral or otherwise."
Slaver: "As long as Follows-Chalk wears his Slave Collar, he'll gain a +10 bonus to his melee skill, as long as he wants to stay on your good side, anyway! Be warned, certain radio frequencies might cause his collar, to well, explode." (this one comes with a bonus C4-style detonator!)
Survivalist: "While Follows-Chalk is a companion, you can ask him to help craft campfire items at any time!"

But, that's not all! There's also four new Challenges, which come with MORE new perks!
Shaken, Not Stirred: "Drink 30 Sierra Madre Martinis with Dean in your party". Gives the player the Glowing One perk (think http://fallout.wikia.com/wiki/Lenny#Behind_the_scenes) when Dean's in the party, which causes Dean to glow and emit a low level of radiation. The upside? All that radiation keeps your energy weapons charged, meaning they burn through their power cells at half the rate!
Challenge #2 (no name yet) requires the player to absorb an ungodly amount of radiation (a bit like the Wasteland Survival Guide quest in Fallout 3), and is unlocked by completing "Shaken, Not Stirred". The perk you get from this one is Cancerous Growth: "Prolonged exposure to Dean Domino's mutation has caused you to mutate as well! When you suffer from Advanced Radiation Poisoning, crippled limbs automatically regenerate. Oh, and you've got a sixth toe. At least it looks like a toe. You might want a doctor to take a look at it."
Fear and Loathing in New Vegas: Drink 30 Datura Teas (a new craftable chem made with Sacred Datura Root) with Chalk in your party", which gives the player an Unnamed Perk, which acts like "Whiskey Rose", except it gives DT when drinking Datura Tea, and ignores the downsides of using addictive meds, instead of Whiskey and alcohol.
With A Little Help From My Friends: Recruit Dean Domino and Follows-Chalk. No perk for this one... yet.

Progress:
About halfway. Dean Domino is complete, except for a little bit of dialogue and a minor AI bug where he won't use the idle marker I want him to before he's recruited. Haven't started on Chalk yet.

Proof of Concept images!
http://i101.photobucket.com/albums/m43/danburite/ScreenShot0-3.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot1-2.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot2-2.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot3-2.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot4-2.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot5-2.jpg
http://i101.photobucket.com/albums/m43/danburite/ScreenShot6-2.jpg

Future Plans:
I wouldn't mind adding Dog/God, Christine, Joshua Graham and Walking Cloud, but with the exception of Dog/God, these guys don't really travel to the Mojave (or at least vaguely "west" in their epilogues). Plus, Dog/God would be really hard to do because of all his personalities.

I always wanted to travel the Mojave with Dean. Wish you good luck!