Here are a few ideas I've been successful with:
Mystery Shopping and Auditing. Two years ago I made over $10,000 by mystery shopping and doing audits of a big electronic store chain. You can learn more at
www.volition.com Besides earning cash, my husband and I had some wonderful dinners out and I also did some jewelry mystery shops and got lots of pricey earrings and charms which I gave as Christmas gifts. You do get better offers if you get certified. Silver certification is $15. Gold is about $99, but you really don't need that for a long time.
Last year I worked for the Census and was fortunate that the man in charge of the office took a liking to me. I ended up working 40 hours a week with occasional overtime and made about $18.50/hr which was a real God-send. They are still hiring for ongoing surveys, but it is part-time, about 20 hours a week. I took a test and we were supposed to start training in March, but were told that until the Feds resolve the budget issues, new hires were on hold. Salaries vary according to your location. The Department of Labor is also hiring part timers to do price audits in stores. Same deal there.
Artisan Preserves are also excellent sellers at Green Markets and flea markets. I forage for beach plums and make jam and an Asian type dipping sauce. Also make other types of jams and salsas, too. Depending on where you live, the process of licensing can be tough or a breeze. Beach plum jam goes for about $10-12 a jar.
You might also make dog treats to sell at flea markets.
Aprons are enjoying a HUGE come back.
I used to sell on eBay specializing in a particular niche, but the fees - including Paypal fees, were out of control. Now I just sell things on my website with an eye towards clearing out all inventory for more room for .... FABRIC! You can also make money on your blog or website with affiliate marketing. You build content with links and get paid commissions monthly. There are lots of them and there is even one for eBay. Yup. You can make money with eBay without selling anything.
Someone mentioned flipping cars. My former neighbor paid off his mortgage buying cars at marshall's auctions and reselling them. Even the beat up ones went fast. During hard times people still need vehicles as station cars, etc. and they don't care what they look like.
Find a niche market. A good friend of mine loves oil lamps. A few years ago I was at a huge estate sale in a warehouse and found several boxes of wicks from the 1940s and sent them to him. One thing led to another and I suggested he start a business selling wicks. Six years and a LOT of hard work later, he just wrote to say he passed the million dollar mark in gross sales.