I buy and sell things in waves on Craigslist as I either get sick of low balling people or people low balling me. Generally, I will browse the free section to see if anything is worth while. I typically look for kids toys (slides, play sets, etc), workout equipment, etc. I also will buy stuff in the video gaming as a package and part it out. I typically buy the stuff pretty cheap and then resell. I shoot for at least a $50 profit on every purchase. I will also buy stuff from sporting goods and baby stuff shooting for $50 profit. In addition to that, I like to browse garage sales and find stuff to flip. On Friday, I bought a leather gun holster, grill set, two pairs of skis with boots, goggles, and poles, slalom ski, and a deer blind for $88. I also picked up a kids wagon, kids slide, and kitchenette from the free section. I hope to sell all this for at least a $300 profit. Items that I've found that sell well for me are kids items (strollers, slides, play sets), video game systems, and sporting goods (especially considering you can usually get a steal; especially in the off season).
Pointers for Craigslist, always start low. Have a limit as to how much you're going to spend (this will depend on your profit margin). Look at comparables of what you're buying to verify whether or not it's a good buy. I typically look at what they're selling for on Craigslist or priced new at Walmart and then list mine for half that being that I generally buy used items. Also, if you can buy package deals and then separate the items, you can probably make a better profit than reselling it as a package. Take good pictures and write a good description. Respond quickly to any adds (this is probably the most important of them all whether buying or selling). Meet in a safe public place and again, meet them immediately if they are willing to buy at your asking price. Use Craigslist to find garage sales in your area and hit a bunch of them up. Hopefully you'll find some decent items and make it worth your time/gas (often times people are selling junk, but you do find some treasures). Lastly, I prefer Craigslist over Ebay due to the fees that Ebay charges for using their services.