I use USERTESTING.com (website testing)
There's less tasks than MTURK, but I prefer the 1 task for 10USD format, with easy Paypal transfers. For amazon.com giftcards, there are a few sites that will allow you to sell your giftcards (RedFlagDeals;Ebay for person to person, and multiple sites that you'd have to pay them a cut and they will sell it for you)