My current hobby is writing simple cardgames in javascript. Currently I have Hearts - http://www.hearts-cardgame.com , Idiot/Shithead http://www.shithead-cardgame.com and Crazy Eights http://crazyeights-cardgame.com .
Am getting my first payout from Google Adsense this month, about 120 $. Which isn't much, but they're pure client side games, require no maintenance or anything so I'll just keep getting a small check every month :)