The TIOBE Programming Community index is a list of the 20 most popular programming languages in use today:
The index is updated once a month. The ratings are based on the world-wide availability of skilled engineers, courses and third party vendors. The popular search engines Google, MSN, and Yahoo! are used to calculate the ratings. Observe that the TPC index is not about the best programming language or the language in which most lines of code have been written.
It should come as no surprise that Java, C, and C++ top the list.
Tip of the hat to Ian Landsman.