Sources for program notes can be found in places such as:
Major orchestras and choral societies often host websites with well-written program notes. A web search for 'program notes' and the name of the piece will usually bring up a number of sites. Many websites have program notes, but as with anything on the Web, consider the source before using the information.
Many program notes are copyright protected. Please be respectful of the works of others and only reproduce those notes where the author has specifically given permission
Musica terna, program notes for 1961-1967 by 
Singer's repertoire by 
Great orchestral music, a treasury of program notes by 
