Writing Prompt Websites

http://www.canteach.ca/elementary/prompts.html
Although not full-fledged prompts, this site includes a list of hundreds of writing topics. With a little revision, these could become prompts, or use them as ideas to spark your writers.

http://www.thewritesource.com/topics.htm
Love this list of writing topics, sorted by grade-level appropriateness. Although not full-fledged prompts, these have potential.

http://www.eduplace.com/kids/hme/k_5/brightideas/index.html
Elementary teachers will love these picture prompts! These help create a visual image in the minds of young writers who struggle to get started.

http://www.doe.in.gov/achievement/assessment/istep-released-items-and-scoring-notes
Select sample items by grade. Remember, you can find not only the hour-long writing prompts, but also the read-write prompts.