Provide a service you will be paid for.. That might be babysitting, mowing lawns, walking dogs (or cleaning out yards where dogs are contained 24/7), cleaning windows, painting garden walls or fences,and elderly folk may need someone to run errands for them , if you live in farming country there may be seasonal jobs where a farmer needs an extra pair of hands, if you live in a tourist area, B and B operators may need extra help, put your name down at local hotels for when they need extra staff for evening parties, weddings or other celebrations. These might not happen every week, but getting known by the hotel as a good worker now may help you get a summer job with them next year.
You have a computer and some time why not try these websites:
http://www.zoombucks.com/index.php?ref=S...
http://www.swagbucks.com/p/register?rb=1...
Each website provides you with $5 dollars just for joining using the link I sent. You can watch videos and earn money or take surveys to earn money. I've already earned $50 this week alone.
Paper boy
some people can get a part time job at your age 15. try seeing whats out there. hope that helps.