Music @ Linux
http://linuxmusician.com
http://sound.condorow.net/ – Sound- & MIDI-Software for Linux
www.hitsquad.com/smm/linux/ – Linux Music Software
www.djcj.org/LAU/guide/ – the Linux Audio User guides
www.midi-howto.com – MIDI-HowTo
Update:
www.linuxsound.at – Sound & MIDI Software For Linux
HOWTO Use MIDI Sequencers With Softsynths
Midi mit Alsa (german)