I just started selling stuff on ebay. Only con that I can think of is they take a cut of what you make. like 9% or something. I'm not sure about amazon. You gott watch out for scammers on ebay and i assume amazon as well. You can also try craigslist but thats just locally. But you get all the money you make and don't have to pay any website.
Ebay dips into your profits and then PayPal does too... taking what turns out to be 15-20% of your profit I've never come across a scammer... but Ebay and PayPal have plenty of buyer and seller protection to keep your ass covered
plus people usually look to those sites for mad deals, so if you don't price it cheap you probably won't sell