What should I do for fundraising for a robotics team?

I am in a robotics team at my high school, and need to raise more than 15,000$ for the team to compete. We have had dinner auction fundraisers, and asked organizations for sponsorship, but thats pretty much all we have.
Any ideas?

Also, as a publicity thing for our team, we are planning to set up booths at local festivals, and possibly sell art to earn a little money (any helps), what possible things can the team make that will look good, not take TOO much time to make, and be profitable?