Apply game mechanics to your app (video)
youtube.com
youtube.com
The best example I know is stackoverflow.com, which uses votes, badges, reputation etc.
Game mechanics are about exploiting irrational but predictable psychological levers in the human mind. To that end, there are lots of apps that use game mechanics, some more obvious than others:
Foursquare/Gowalla are obvious. You get random rewards and points for doing various real-life activities like traveling and eating out.
Opower. See, e.g., this article http://latimesblogs.latimes.com/greenspace/2009/10/californi...
Mechanical Turk. Why would an American do work for $0.50/hour? It's not rational, and I think it's the game-like nature of mturk.
Many websites use the quest/reward mechanic to guide users through the registration process and the first few key steps of the application, e.g., LinkedIn's "your profile is 75%" complete mechanic.
I think the issue is more about providing a meta-experience as games do rather than the particulars of the game mechanics.
Weight Watchers uses game mechanics: http://www.wired.com/gaming/virtualworlds/commentary/games/2...
Mint was experimenting with it: http://www.techcrunch.com/2009/04/28/mint-turns-personal-fin...
They're building achievements into the new Honda Insight: http://www.popsci.com/cars/article/2009-02/eco-drivers-ed-20...
Yahoo calls them Reputation Design Patterns: http://developer.yahoo.com/ypatterns/social/people/reputatio...
They work. My company provides game mechanics as a service that can be integrated into any site or application: http://www.bunchball.com/products/nitroworks.shtml
Some of our customer sites that are using game mechanics successfully: http://www.warnerbros.com/loyalty - WB loyalty program http://www.espin.com - social network for teens http://www.dundermifflininfinity.com - NBC's social network for fans of The Office http://www.characterarcade.com/ - USA Network's casual gaming site.
You can see a video of me talking (very fast, for 23 minutes) about how this stuff works here: http://xmedialab.tv/auckland-%E2%80%9Ccommercialising-ideas%... - click on "Rajat Paharia presentation"
I tweet examples whenever I come across them here: http://twitter.com/bunchball