The classifieds are a big buy and sell; individual sellers may accept any combination of Paypal, email money transfer, direct deposit, and the like. EMT seems quite popular.
Most of the retailers are similar to this.
As to getting scammed, you should be pretty safe. There's a feedback system in place for all users (notice it under a user's name on any of their posts) that lets you know the experiences other people have had dealing with a buyer or a seller. I've not personally had any issues in my few transactions here since I was AVed. I've seen a couple of disputes pop up, but they seem to have been resolved.