There's an interesting piece on the 10 Programming Languages You Should Learn Right Now.

The article compares the number of available jobs against the different programming languages. There's an interesting mix here, and four of those quoted are directly open source, including the big three (Perl, PHP and Python) and of course Ruby.

My only criticism of the article is that it quotes AJAX as a language (it isn't, it's a technology, and you can do AJAX with Javascript and just about any backend language you like); and Ruby on Rails is a web environment for Ruby, and probably shouldn't be considered as a different entity (they both get the same ranking).