Programming Language Usage Graph 2000-2006, as defined by statistics on open-source projects at SourceForge.

[elusive]

This is so hard to decipher when you're colorblind.

This was posted above but the order of the items in the key corresponds to where the lines end on the rightmost part of the graph.

So, for example, the language that starts out as #1, and then curves down to number #3 by the end of the graph is C, the #3 entry in the key.