I have found this website that looks good for a variety of reasons. Others who teach writing may be familiar with it. It includes lesson plans, publishes student writing, and lists resources that may be used in the writing process. I use it regularly in my math lessons. Virtually every math topic is covered and the range is from primary to high school.
Popular books are also topics with math problems to go along with the story.
You can enter any words from spelling, literature, science, social studies, or math. A puzzle will then be generated for you to print and share with students. I have a web site that I think is neat for anyone doing a space unit. It is an on-line service for teachers, students and parents. It also allows teachers to post their classroom assignments on the Internet.