Arab music reference materials
Text
The Garland Encyclopedia of World Music online (see especially Volume 6). Also see the offline versions; not everything was included online.
Grove Music Online (not currently available off-campus)
Wikipedia articles on Arab music
Maqamworld: Theory and instruments (superb site!)
Audio
Various Arab music audio sites
Contemporary World Music (full audio database)
Smithsonian Global Sound (full audio database)
Smithsonian Folkways recordings (with 30 second clips and liner notes)