More creative (than mine) uses for blogs, from Willamette Aspire '10:

Post Lessons
Get to Know Students
Communicate with other classes
Communicate with other countries - for class projects
Online Journal for students - reflection on class activities
Calendar updates for events, etc.
Specific links for research activities
Assignment list - links to homework handouts, etc
Reflective blog throughout a course - weekly reflections
Picture Diary for the class
Parent Involvement - instead of newsletter (kids write the articles!)