I recently ran across a couple of very cool sites for vintage downloads.
First is this one, Vintage Arab Pop Music.
It is mp3s of 50+ 78s from the 1930s-1950s. Unfortunately the person who has posted them does not read Arabic, and some labels do not use Latin characters. There is some wonderful stuff here from well-known artists like Mohamed Abdel-Wahab, Umm Kalsoum, Sabah and Fayrouz -- and a lot by artists I did not know. A great source to explore.
The tracks I found most interesting were two by Hanan and Fayrouz (yes, the Fayrouz). In English they are identified only as "Swing" and "Rhumba."
The Arabic lyrics for "Ghayb ya 'amr" can be found here. (I think the translation is more or less, disappear, O moon, but hopefully someone who reads this will come up with a more colloquial translation.)
The other site is Naksh al-sanadeeq.
This is tumblr account so new stuff keeps showing up. It's a pretty wide variety, stuff like Sayid Darwish, Warda, Nass El Ghiwane, and so on.
But it's what you might not have heard of before that might be the most interesting. I'd never heard of the Syrian singer Mayada El Hennawi before, and I just love this album of hers: Moush Aweidak/Ashwak.
And I had never before heard Egyptian composer Riad el Soumbati performing his composition Al-Atlal, made famous of course by Umm Kalthoum. His version is great, fabulous oud playing.
One warning about this site: some of the records are scratched and skip or stick...But ma'leesh.