The MSQ Project - Description of the MSQ file format and MSQ tools, which include MSQ to MIDI and MIDI to MSQ converters. - http://www.aconnect.de/friends/msq2/msq.htm
The MIDI Farm - A starting place for up-to-date information on current MIDI based music composition products. - http://www.midifarm.com
The MIDI Specification - A free version of the MIDI Specification. - http://www.borg.com/~jglatt/tech/midispec/intro
Knowledge Hound: MIDI - List of links to MIDI tutorials and resources. Suitable for beginners and advanced users. - http://www.knowledgehound.com/topics/midi.htm
MIDI Manufacturers Association Incorporated (MMA) - Formed to maintain the MIDI specification as an open standard. The site contains the MIDI specifications, information about the MMA and news related to MIDI and the MMA. Part of the website is members only. - http://www.midi.org/