There have been a number of original novels based on High School Musical, as listed below:

#1 Battle of the Bands - N.B. Grace (January 16, 2007)
#2 Wildcat Spirit - Catherine Hapka (March 20, 2007)
#3 Poetry in Motion - Alice Alfonsi (May 22, 2007)
#4 Crunch Time - N.B. Grace (July 31, 2007)
#5 Broadway Dreams - N.B. Grace (September 25, 2007)
#6 Heart to Heart - Helen Perelman (November 27, 2007)
#7 Friends 4Ever? - Catherine Hapka (February 26, 2008)
#8 Get Your Vote On! - Alice Alfonsi (April 22, 2008)
#9 Ringin' It In - N.B. Grace (August 26, 2008)

   

The movies High School Musical, High School Musical 2 and High School Musical 3: Senior Year have also been made into Junior Novels:

High School Musical: the Junior Novel - Released June 1, 2006
High School Musical 2: the Junior Novel - Released August 14, 2007
High School Musical 3: Senior Year: the Junior Novel - Released October 2008