A good starting place for Judeo-Sufi studies...

Rabbeinu Bachya ibn Paqudah's Duties of the Hearts. Known in Arabic as Al-Hidayah ila Fara'id al-Qulub. In the Hebrew translation from the Judeo-Arabic, it is known as Chovot ha'Levavot, a text studied in Orthodox Yeshivot still today.

http://www.amazon.com/Direction-Duties-Littman-Library-Civilization/dp/1904113230

The next book, Al-Bustan al-`Uqul (The Garden of Intellectual-Reasonings) is Rabbi Natanyel ibn al-Fayyumi. Like rabbeinu Bachya, he was a Neo-Platonist, influenced by the Ikhwan as-Safa and was also the head of the Jews of Yemen the generation before the Rambam. The Epistle to Yemen was to this man's son, one of several significant reasons arguing for its lack of total historicity...

http://www.amazon.com/Bustan-al-Ukul-Nathanael-ben-Fayyumi/dp/0543712834/ref=sr_1_fkmr0_1?ie=UTF8&qid=1284477209&sr=1-1-fkmr0

The son of the Rambam, Avraham ben Maimonides, authored the Kitaab Kifayat al-`Abideen, (Comprehensive Guide to the Servants), a book which famously praised the Sufis of Islaam and called for the readoption of their ancient Jewish practices by the Egyptian Jewish community which he led. This is actually a very bad translation and not even the whole book. This was translated from the HEBREW translation from the Judeo-Arabic, and as i said, it is not even the whole thing. But the Judeo-Arabic translation is very long out of print. i have a copy that my son is scanning in, but it's not ready yet (still a lot to scan).

http://www.amazon.com/Guide-Serving-Torah-Classics-Library/dp/1583309810/ref=sr_1_1?s=books&ie=UTF8&qid=1284477257&sr=1-1

`Ovadyah ben Avraham ben Maimonides wrote an excellent Judeo-Sufi Treatise on the Pool, in Judeo-Arabic: Al-Mawalah al-Hawdiyyah

http://www.amazon.com/Treatise-Pool-Al-Mawala-Al-Hawdiyya/dp/0900860871/ref=sr_1_1?ie=UTF8&s=books&qid=1284477473&sr=1-1-spell