before trying out a simple home built programmer i would recommend that you check the amount of frustration that people get from these simple programmers. you can have a look at the AVRfreaks forum. buying a "proper" programmer will be money well spent!
and building a multipurpose programmer isnt recommended either. you see those multi-purpose tools in the hardware stores? they wear out quickly so it is better if you buy separate tools for separate jobs. same is the case with programmers and stuff like that.