There aren't actually a lot of open source bugs that bother me that anyone here can fix. If you go on Launchpad, for instance, you'll see that the majority of important bugs relate to hardware compatability, Flash, and WiFi firmware. 
However, if we can call features a bug, I would really like some better graphical frameworks for HTML5 a-la Flixel or Flashpunk for Flash. As a game developer, I would love this, even if it's simple or bare bones, as it would send me in the right direction and show me some best practices.
I'm running through digging out a plan of action - this was the 2nd in the list at the chosen moment in time. I don't know what specific action we could take with the HTML5 idea within the budget - do you have any ideas?