The iPad/Arduino powered Kegmate at Yelp[1] is the result of a Hackathon, which are regularly scheduled. The most recent one was expanded to two days because we found that one day just wasn't enough. It's a lot of fun and many people work straight through to power through implementing their ideas. A lot of interesting, good things have come out of these events. You can work on <i>anything</i>, you need to present it to all the other engineers at the end, and we encourage you to work with people from other teams that you might not normally get a chance to work with. For weeks before hand, people are coming up with ideas, drumming up support/finding other people who are interested in the same idea to work with, and judging effort to make sure they are working on something can be demoable at the end. I got a chance to get involved with doing some embedded development, which I'm interested in but don't normally get a chance to work on.<p>There's been a lot of fun things, and a lot of productive things. From Kegmate to a MUD that simulated the office environment to unexpected reporting tools that help out other departments.<p>[1] <a href="http://engineeringblog.yelp.com/2010/08/yelp-makes-beer-more-fun.html" rel="nofollow">http://engineeringblog.yelp.com/2010/08/yelp-makes-beer-more...</a> (previously posted on hacker news)
Can you spend your Twitter/Google 20% time doing something non-technical that matters to you or your community? Like helping out a local charity, drinking beer, or gardening for your disabled neighbour?
Note that one week a year is actually... 2% time. A full 20% would work out to about 2 and a third months a year. Regular "hack" time and private project time is good, but 20% time is so quantitatively different that it's fundamentally qualitatively different as well.