I bought my current wheels off of Craigslist, but I did run into a bit of a hiccup - One of them had a short crack on the lip and the previous owner had tried to hide it with JB Weld.. and I missed it when I was looking them over. Discount Tire pointed it out to me when I tried to get them to mount the tires on the wheels.
I was lucky enough to find a top-notch welder here who specializes in aluminum and alloy welding. He did an amazing job and the wheels are good, but I definitely dodged a bullet.
My big caveat when looking for wheels on Craigslist is to do extra due diligence and make sure you inspect the wheels super close. IMHO, CL is worth looking at, but really only if you can get them cheap. I got these ones for cheap, but if I had known about the crack before I paid for them, I would have just skipped them and kept looking.
My main go-to nowadays is DT, DTD, and Tire Rack.