Comparing Synchronous Technology

This is a very nice summary of the use of tools in online education.  Hrastinski summarizes the pros and cons well.

Asynchronous and Synchronous E-Learning (EDUCAUSE Quarterly) | EDUCAUSE
CONNECT  EDUCAUSE Quarterly, vol. 31, no. 4 (October–December 2008)

When, Why, and How to Use Asynchronous vs. Synchronous E-Learning
	Asynchronous E-Learning	Synchronous E-Learning
When?	Reflecting on complex issues n When synchronous meetings cannot be scheduled because of work, family, and other commitments	Discussing less complex issues Getting acquainted Planning tasks
Why?	Students have more time to reflect because the sender does not expect an immediate answer.	Students become more committed and motivated because a quick response is expected.
How?	Use asynchronous means such as e-mail, discussion boards, and blogs.	Use synchronous means such as videoconferencing, instant messaging and chat, and complement with face-to-face meetings.
Examples	Students expected to reflect individually on course topics may be asked to maintain a blog. Students expected to share reflections regarding course topics and critically assess their peers’ ideas may be asked to participate in online discussions on a discussion board.	Students expected to work in groups may be advised to use instant messaging as support for getting to know each other, exchanging ideas, and planning tasks. A teacher who wants to present concepts from the literature in a simplified way might give an online lecture by videoconferencing.