Lists seem to be popping up everywhere on how to create a good webinar...there are so many good suggestions in them. Here's one from TechSoup that a friend forwarded to me today.
http://www.techsoup.org/learningcenter/training/page11252.cfm
The authors make a lot of good points. I am surprised, however, that the article states that a webinar should be kept to under 2 hours. That seems very long to me. I would recommend under an hour and really try for a 45 minute presentation with a 15 minute question/answer period.
There's a great link in the article that connects to a recorded webinar, Getting to Know Online Conferencing Tools, in which Laura Quinn from Idealware discusses various online conferencing tools and their appropriate applications. Online Conferencing has a lot of players in it at the moment, it will be interesting to see how the market shakes out. This is a rapidly changing environment with a lot of creative solutions offered but consolidation and restructuring is bound to happen eventually.