Just thought I'd revive a couple of dead threads and mash them together.
First, I would borrow the time machine from the outhouse thread mentioned above, travel back in time and give myself a good kick in the rear along with the idea to get a degree in structural engineering.
Armed with my useful knowledge and the profits from some "lucky" investments, I would buy neglected old houses and return them to their former glory, starting with my great-grandparents gothic style farmhouse and my great-great-great-grandfather's log cabin.
I have to say that going back in time and giving previous self a kick would definately be how i would use a time machie. My parents always wanted to buy me a run down place for me to do up and live in when I was at uni with my uni mates paying me rent. If only I had listened to them!!
Dream project would be a 500ish gallon salt water fish tank. I would love to have one big enough to have a stingray and some small sharks. Would be pretty expensive and my biggest drawback right now is convincing my wife. Don't think she likes the idea of having that much water in our basement.