Tollefson of Berkeley has put together some good ideas for assignments in his “Encouraging Student Writing.”
I particularly like:
Book Review for a Professional Journal
After perusing an appropriate journal to identify the format and approach of typical book reviews, students can practice their skills in summarizing and placing material in the context of related reading and research by writing a book review for a professional audience.
and
Letter to a Public Official or Company Officer
Writing a persuasive letter, arguing for or against a particular policy, requires students to organize their case from the policymaker’s perspective, decide the best way to present supporting evidence, and anticipate and respond to counter arguments.