This is an excellent idea. I had a friend who was doing this, and her rewards were new shoes or clothing for her goals! Her husband worked out a rewards system with her and she'd get to buy something for every like 5lbs she lst. This worked really well for her because she was a total shoe and clothes lover!! (like a lot of women. hehe)
So.. here are some of my rewards
First 5lbs, I bought a new pair of shoes and jeans, desperately needed!
I think a real key here is finding something that you would really enjoy having or appreciate doing for yourself. Perhaps something you haven't done in a really long time and then rewarding yourself with that.

Also. posting pictures up of what your "starting weight" is at your house is another good motivator. This way you can have a reminder of just how far you have come and where your still getting to!
Some other reward ideas:
New work out clothes
New work out dvd
new work out accessories (i.e. I Just bought a new water bottle!! which I'm excited about..what a nerd!)
new pair of tennis shoes
flowers for yourself
Another note.. most of you probably know this, but to state the obvious, just do not reward yourself with food. As it is our whole
goal to teach ourselves that food is not our gratification. Its fuel to keep our bodies going and that's about it. (At least its how I need to remind myself)
Secondly.. for motivation, practice some "positive self talk". Make a
goal every day to say one positive thing about your progress, your success, and your goals.

Whether it be work, your
dieting, your exercise, whatever..

Mine for the day is: Even though I desperately do not want to exercise anymore this week, I got up this morning and still hit the
gym. I will be exercising tonight. Yay for me!
Hope.. my lil tid bits help someone!!