I've been looking into making a solar oven and solar food dryer, and have been very impressed with both the cost and the effectiveness. I'm a member of the Solar Cooking group on Yahoo, and have been following the use and testing of a few that I had considered. One member, Ken, made this video that has truly convinced me that I MUST try one this year!!
I'm so impressed with the temp outside and how well it does - even with snow on the ground. At $5 a gallon for propane, this certainly will pay for itself quickly.