python

GnuCash is an excellent linux based accounting package, it is modelled very closely to traditional two-column accounting methods but has lots of functionality like generating invoices, tracking clients and all the other things you'de expect from a package to run your finances.

Something I wrote for a small project, initially designed to listen my radio scanner via /dev/dsp and record when it hears something, this uses python and some threads to launch instances of 'lame' encoder and then insert them into MySQL.

The app has a threshold for incomming sound levels and starts recording when the threshold is reached, there is also a setting for time-distance between hearing things so you dont end up a billion little mp3s because the audio is dropping out, just a nice long mp3.