Tim O'Reilly has another great roundup showing sales of computer books. The numbers give a great idea of not only current market share in terms of categories/subjects, but also of the trending for the various subjects.
Particularly of note? Ruby, Rails and Javascript are absolutely exploding. With Ruby book sales growing 733% over the past year! Consider, also, that currently there aren't that many titles available which address the Ruby or Rails markets. The numbers should continue to grow and impress when we see all the currently in-development Rails books hit the market.
Those looking to raise the ire of Python programmers can now gloat - The ruby market for books is now larger than Python; though both are still less than Perl, which gives a good relative idea of market size (and makes me weep - Perl is dead!).
PostgreSQL also seems to be growing more briskly among the database category, while MySQL declines modestly. I guess that's good news for Robby.