Hi,
this is not a hack, but it makes a lot of fun to play with.
Sphinx is a speech recognizer written entirely in Java.
It's easy to write new programs using this package (see Demos)
and use your voice as an input to control it.
It works fine with Linux and doesn't need much configuration.
And the recognition even works fine with my foreign accent.
Together with the festival TTS System I wrote a program for
Monkey Island's insult swordfighting :-).
Homepage:
http://cmusphinx.sourceforge.net/sphinx4/
Demos:
http://cmusphinx.sourceforge.net/sphinx4/#demos