As Big Booger mentioned in this thread: http://www.techzonez.com/forums/showthread.php?t=15525 Tux Magazine did an article on a Drum Machine software package that has been created for Linux, Mac OSX, and for Windows. And it's all free...
Here is a link to their wiki for more info: http://devel.hydrogen-music.org/wiki/
Hydrogen is an advanced drum machine for GNU/Linux. It's main goal is to bring professional yet simple and intuitive pattern-based drum programming.
Some of the features
* Very user-friendly, modular, fast and intuitive graphical interface based on QT 3.
* Sample-based stereo audio engine, with import of sound samples in .wav, .au and .aiff formats.
* Support of samples in compressed FLAC file.
Sequencer and mixer
* Pattern-based sequencer, with unlimited number of patterns and ability to chain patterns into a song.
* Up to 64 ticks per pattern with individual level per event and variable pattern length.
* 32 instrument tracks with volume, mute, solo, pan capabilities.
* Multi layer support for instruments (up to 16 samples for each instrument).
* Ability to import/export song files.
* Unique human velocity, human time, pitch and swing functions.
* Multiple patterns playing at once.
* JACK, ALSA, PortAudio and OSS audio drivers.
* ALSA MIDI and PortMidi input with assignable midi-in channel (1..16, ALL).
* Import/export of drumkits.
* Export song to wav file.
* Export song to midi file.
*Again this is a free drum machine for all platforms. Some of our musicians should check it out!*