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Just check the upcoming camps and see if there is some group conducting the camp in your city/area. Just add your name, details about you and your project and join the group on the specified date.
Any project that you are interested/love to do. It can be anything like a web application you wanted to build, compiler for some obscure language, painting/sketching, fixing roads, a neat mechanical contraception or even a rocket etc. The important thing is to get it to a state which you can show/work with.
Your wish. You can do it alone or team up with your friends.
24 hours is sufficient enough for kickstarting your project. The time constraint will make sure you prioritize your goals and complete the most important task first.