I listened to a fascinating interview with Dr. Maria Anderson of Muskegen Community College on teaching calculus online. Maria uses Twitter to form a community both for its immediacy and its ease of use. She comments that it can be easy to get a little detached from exactly what the students are working on at any one time. To combat this she asks them to tweet a minimum of ten times a week with what they are learning.
The class uses Jing to post their work, so they can show work without fussing with math and the keyboard.
The interview includes a discussion of how Dr. Anderson uses the discussion boards and why she uses old-fashioned paper and pencil proctored exams.
Well worth your 1/2 hour: http://teachingcollegemath.com/2011/08/podcast-interview-about-teaching-online-calculus/