A Little Gift by
Mice1900.
This is my all time favorite of the threesome fics. It's Rodney/Carson/John, NC-17. It's very well written and the boys never seem out of character. I love the flow of the fic and particularly, the beginning of the fic when all three are on the couch. It's got some cute dialogue and Carson's reaction is perfect.
Also - make sure to read the ending. *g*