Given the proliferation of "X for Y developers" books, I decided to collect some information to help me find a niche for my own book!
This table shows the number of combined Google hits for "X for Y developers" and "X for Y programmers", with a selection of Xs and Ys (e.g., the first rows shows the hits for "BASIC for BASIC developers", "BASIC for C++ developers", etc.):
It looks like we're missing a good "Cobol for BASIC programmers" book: I'll start typing right away!
Note that the matrix is highly asymmetric: apparently, Perl programmers are more interested to switch to Python than vice versa. We can turn the entries of the matrix into weights in a directed graph, that can be loosely interpreted as the relative number of people that would like to switch from a programming language to another. Below you can see the graphs for six of the languages (the size of the arrows correspond to one of 6 bins of equal size on a logarithmic scale; no arrow means zero results):
In case you were wondering: yes, there really is a successful "Java for Cobol programmers" book!
Update 1 Apr 2012: Added values for Fortran to the table.
I haven't tried the game on Safari or Opera, please let me know if it works!
I set up a github repository for the source code and other material published here. It's a much more convenient way to share source code than uploading archive files.
You can find it at http://github.com/pberkes/masterbaboon . Enjoy!