TIOBE index
Tiobe programming community index is an ordered list of programming languages, sorted by the frequency of web search using the name of this language as keyword. The index covers searches in Google, Google Blogs, MSN, Yahoo!, Wikipedia and YouTube. The index is updated once a month. The current information is free but the long term statistics over many years of observation is for sale.
According the site, Tiobe index is not about the best programming language or the language in which most lines of code have been written[1]. However the site claims the frequency of searches may reflect the number of skilled engineers, courses and jobs worldwide. These claims are criticized in the opposing publications[2]. In particular, decrease of Perl popularity (while it is in general not ranked very low) raised discussions that maybe this language is "dying" [3], followed by wide negative response from the Perl community [4].
As of 2009, Tiobe currently lists Java and C as the most popular targets.