I saw one set of 5 cds on flipkart sometime back. the name of the album is Sufiaana i think. It has traditional sufi as well as the modern one including few sufi touch tracks from bollywood movies.
'Teri Diwani' is a good collection of sufi songs from bollywood movies. There are a large number of collections of Nausrat Fateh Ali Khan - you could start out with his greatest hits collections. Ditto for Rahat Fateh Ali Khan