When you're bored and looking for a quick project to make money, you can leverage this network you've built to find projects quickly.
There are also a slew of websites for freelancers that might be more targeted than Craigslist for what you need. Try searching for these services (can't remember what they are off the top of my head, sorry).
Still, that's probably your best bet. Some are fakes, that's true, but some are real and if you're not getting a single response, your pitch might be off. You certainly don't want to say "I'm a student and have 6 weeks off and I'm bored". Maybe post what you are saying and we could critique.
Longer term, you may want to pick up small projects through grad school. I know I did even in undergrad. That requires networking as the OP said. Once you've done a few gigs (and done them well) you tend to get repeat clients that can sustain you and referrals.
You might have better luck at sites like Elance instead of Craiglist. I think you would deal with less flakes.
Personally every contract and job I have had was found through my network. Find your local tech groups and start getting to know people and let them know you are looking for some short term work.
best of luck