The Popularity of Programming Languages

This link is the TIOBE Programming Community index which is an indicator of the popularity of programming languages. The index is updated once a month.
http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

This is another useful link to compare different programming languages.

http://www.ohloh.net/languages/compare?measure=commits&percent=true&l0=-1&l1=csharp&l2=cpp&l3=java&l4=pascal&l5=visualbasic&l6=-1&commit=Update