Worksheets should be kept to a minimum, but they can be helpful on occasion for the teacher to assess what the students have mastered individually and as a group. They also can allow time for the teacher to meet students individually in the hall to check their range, pitch matching, or ability to sing a given tune. Some ideas for written work are for students to:
Write the rhythm of a given song under or inside hearts drawn on the handout.
Given a rhythmic line and meter, draw bar lines and write the subdivision, labeling form.
Write names of black and white notes on a paper piano keyboard.
Given ten hymn numbers, write the key, beginning melody note, and solfege of first note.
Write down hymn numbers written in a given key.

Websites for Worksheets
http://www.makingmusicfun.net/
http://learnmusictheory.net/fundamentals/index.asp
http://www.finalemusic.com/finale/features/educatortools/worksheets.aspx