An obvious one is hgtv. I think they are currently launching a dream home give away contest. Although, I think that's a little different than what you mean. However, here's the link:
You could also try a site called Furniture for Small Spaces. They're doing a small contest for people who have small bedrooms. The rewards are much smaller but the chance of winning is much greater and it might be fun to enter:
If those aren't enough, you could also try contest directories. They usually have a section for the home which might list other contests.
I hope that helped!
Furniture for Small Spaces