Spelling
Spelling City

Reading
Raz-Kids
Starfall
Jan Brett

Here is a website that is excellent in helping parents find book titles that libraries house or the local book store.  The book titles are listed by reading levels. 

http://home.comcast.net/~ngiansante/

Math
Everyday Math Family Letters
Everyday Math Links

Computer Skills
Bees and Honey

Social Studies
Thanksgiving

Science
Zoobooks
Properties