GitHub blog shares some trends in regards to programming languages, which includes both public and private repositories:
Interesting. I haven’t seen many Java and C# projects myself, but I’m in a very different bubble. PHP stays on #4 for years. VimL, the language in which most plugins for Vim editor are written, makes it to #10 in 2010, which suggests that there are way more plugins than I ever thought. The drop in Perl is also quite notable, but not very surprising.