I don't own any projects on GitHub but I occasionally fix bugs in projects that I am using.
Before I setup my GitHub account I made some fixes and enhancements to ActiveMerchant. http://markmail.org/search/?q=primerano+activemerchant
At some point I'll start a project on GitHub but I'm not going to start one for the sake of having one.
A trivial yet useful thing I wrote was a referrer hider for MediaWiki. http://www.mediawiki.org/wiki/Extension:HideReferringPage
The story of why I wrote this is here
I have also wrote a WordPress plugin for Geoskipper.