I just had the interesting experience of giving a presentation (at Computers, Freedom and Privacy 2008) by Skype video. It seemed to work well — with minimal technical difficulty, we had a reasonably interactive panel discussion as well as my talking through my slides. It saved me two days of travelling; 1.3 tonnes of CO2 emissions; and having my photo and fingerprints taken by US Customs. Of course, I miss the opportunity to now go for a drink with the panel and audience :)
I'm also experimenting with SlideShare. Thanks to them you can see my presentation below (on proposals for "three-strikes" legislation that would force ISPs to terminate the accounts of alleged copyright infringers). All comments welcome!