Yesterday I helped someone write their first WordPress core bug report, and then someone else write their first patch to fix that bug.
It happened after I saw a thread in a Facebook group about an issue with WordPress 3.8.
Turns out this was a bug I was responsible for (doh!), but instead of just fixing it, I offered to tutor anyone interested in how to create a bug report and write their first patch.
Revital and Niv jumped on the offer, and so we chatted about how to test and confirm the bug, and how to write a good bug report. Then we followed with installing WordPress via SVN, running the new build process, and generating a patch.
WordPress just gained two new contributors, and this is probably the most meaningful thing I did all week.