On: Ask YC: list of what languages sites are written in?

[byrneseyeview]

"My whirlwind tour will cover C, C++, Lisp, Java, Perl, (all languages we use at Amazon)..."

http://steve.yegge.googlepages.com/tour-de-babel

Other than that, I'm not sure. I heard that eBay uses C#, though.

If you want to put this together, I would recommend looking at their job ads.