FWIW, helping with the mentoring.is page (albeit a small project) is what got me started about this whole topic. I've been talking with a couple of mentors (who are heavily involved in open source themselves) about how I can contribute to some of my favourite projects, and it's definitely something I plan to do as I get free time.
For example, I organized and developed the http://www.thisisthecountdown.com event for the recent Ubuntu release as a volunteer project. While the response was mostly well received, there were very harsh remarks by some people directed at the site.
Sorry, I didn't quite grasp what you were implying earlier. I didn't realize that you were a fan of the mentoring.is project and then offered them your help (which is what I was encouraging you to do), I thought you had just set up a mentoring page for yourself (which seemed unrelated).