It wasn't all that technically challenging, but we've just soft-launched our mobile app deal platform at AppDiem.com.
The premise is simple enough -- it's basically Groupon (or maybe Woot) for mobile apps. There are a ton of warts at the moment, and I'm working on them, but I'd love any feedback from you guys.
The platform is Django, with a tiny little bit of celery+rabbit to move some of the slower tasks into the background.