I came across Crowdtap while reading the "generosity project" blog.  Here is what the blog author says about Crowdtap:

Crowdtap is a marketing themed social game, integrated with Facebook, that let's members showcase their marketing skills with brands, acquiring points that build their status, and earning cash for gift cards and charity. From answering quick polls, ideating on marketing approaches and evaluating creative to sampling new products and throwing branded parties with their friends, Crowdtap provides a unique blend of online gaming paired with real world challenges. Participation is free, fun and rewarding.

It is still in beta and I am not very 'into it' just yet, but more exploring to come.