A long time ago, we posted Tiobe index listings on a regular basis. The Tiobe indexes showed the popularity of programming languages in the industry. You can see their site for specifics on how the measure popularity, but in short it centers on searching and other factors.
Each month a new update is posted. Most recently it has been interesting to watch as C and Java have vied for the top spot. While the last couple of months Java has taken the top position, earlier this year C was on top. The following slides show the charts from Tiobe Software for some of the top languages used by members of Codeguru.