Does anybody rent/trade anymore?

So I like gaming but I don't like paying $40-$60 for a game I am going to play for 2-3 weeks and then sell on eBay for next to nothing. I haven't looked around too much but before I do I was wondering if anyone had an suggestions on where to get games from for not a lot of money and be able to either trade them or return them after a month or so. I know of GameFly but I have heard A LOT of mixed/bad reviews about them and getting decent games. So my question is, is there anywhere that either lets you rent/trade games with other people? I am an achievement whore so this is mostly why I am asking and also because sometimes a game is only good for one play through and I cannot justify paying even $30 for a game I am going to beat once and then be done with. Any suggestions are welcome.