Encyclopedia of Contemporary Christian Music
I've got a different sort of recommendation.
Last month, I mail-ordered a cheap used copy of Encyclopedia of Contemporary Christian Music by Mark Allen Powell. It was published in 2002 and came with a CD-ROM with the book in a big PDF file.
The book isn't perfect. Its a few years out of date, there are a few omissions (particularly Christ Tree by The Trees Community), and the author (a theologian) likes to criticize songs where he doesn't agree with the theology. For example, he manages to bad-mouth the song "Shotgun Angel" in three different artist entries. He does call things as he sees them, and isn't shy about covering scandals involving CCM figures.
On the plus side, as with the best of music books, it has inspired me to purchase music. I've been purchasing lots of cheap CDs based on what I've read, such as a 99 cent Aaron Sprinkle CD at a local store last week. I've ordered about 10 CDs for $2 or less from Half.com, and added a pile to my wish list to watch for cheap copies in the future. Dietiphobia, Atomic Opera, Caedmon's Call, Paul Colman Trio, Phil Keaggy, Charlie Peacock, The Prayer Chain, Fleming & John, Jars of Clay, Vigilantes of Love, The Aunt Bettys, Rick Altizer, and so on.
Too much music for me to process and recommend, but I can recommend the book for anyone wanting to delve farther into Jesus Music, Christian Rock, and other CCM.