http://www.youtube.com/watch?v=NWHfY_lvKIQ
Joel shows that StackOverflow is (||was?) running on 2 servers (+1 backup) using C# and SQL Server. Impressive :-) seek to 24:56 to see the full performance+tech table.
There is also a Perl+Perl6 mentioned in this talk, seek to 38:00 to hear the #1 thing you should never do...
