Playing games online: if you like playing games, why not turn the hobby into a moneymaking activity? There are tons of websites out there that reward their loyal fan base with points when the complete a game or play for a certain amount of time. These points can then be exchanged for real money. Sites are able to do this by sharing the profit they make from ads as an incentive for users to visit the site.
Another way survey packages can make it easier to track different groups of respondents is via multiple "collector" links. These are simply different links to the same survey that can be broken out in analysis later. For example, if you wanted to field a survey to both Facebook and Twitter users, then posting different collector links on each network would let you track from which social network different respondents came.