Swagbucks* is a fun survey site that pays you for completing short online tasks in virtual cash - you can then exchange this for real money, Paypal credits or gift cards to spend at Amazon, M&S and more. The site's huge in America, and here in the UK many MSE forumites are dedicated users.
Tasks include filling in polls, watching videos and searching using its page instead of Google. Advertisers pay Swagbucks to publicise their wares or do market research, and the site passes a cut to you. The more dedicated you are, the more you earn, though every task pays a different amount.