Well, we don't have a song fest, but we do have a Mock Rock at the end of Derby Days in the fall, and something called "all-house sing" during Greek Week.
For the DD Mock Rock, all the sororities basically create elaborate dance routines. Just about everyone in the house is involved, along with the houses three Derby Days "coaches". We usually get very elaborate with the 'technical' aspect of our Mock Rock. Last fall, we used a Missy Elliot song, and the year before, we used a portion of a Michael Jackson concert. In my opinion, they both turned out pretty well, although we didn't 'win' either year.
For GW "all-house sing", all the sororities take a song (or several songs) and change the words to involve their house and Greek Week.... Since I've been there, we've done Girls Just Wanna Have Fun (Pi Phis Just Wanna Have Fun) Sugar Pie Honey Bunch (Sugar Pi Beta Phi) and Hey Ya. We do this in the gym and it's not nearly as elaborate as Mock Rock.
Ah, Recruitment skits.... For years and years, our chapter did "Grease", but the year I went through recruitment was the last year we used it. Since then, we've been doing a skit we call "Pi Phi Scrapbook", but that is getting out of hand. Our recruitment chair is currently looking for a new skit.... We're thinking about a "Wizard of Oz" thing, I believe.