Arab music reference materials
Library, web, and wiki resources
NITLE project contains a number of music resources, mainly here.
The Garland Encyclopedia of World Music online (see especially Volume 6). Also see the offline versions; not everything was included online.
Maqamworld: Theory and instruments (superb site!)
Collaborative reference projects
We can edit the following pages together:
Arab music URLs. A list of relevant links.
Wikipedia articles on Arab music. A collection of what wikipedia has to offer.