If you are creating a presentation then generally most people use PowerPoint. Personally I now create virtually all my presentations using Apple’s Keynote. One of the many reasons I like Keynote is the way it handles images, audio and video compared to PowerPoint.
One of the features of Keynote that I have always liked is the ability to save a presentation as a movie file. As once a movie file it can be converted in many different ways. For a JISC online conference I did this and then converted into multiple mobile formats. Of course once a movie file you could upload your presentation to YouTube.
In version 4.0 of Keynote (part of iWork ’08) you can now send your presentation direct to YouTube.
This avoids the need to export the file and then upload to YouTube, you can upload direct to YouTube quickly and easily.
I’ve not yet tried it, but I can see after attending a conference I could upload my presentation and then embed it into my blog or the organisers could embed into their website. It also avoids the problems that you can have with Keynote files as not everyone has Keynote and even if you export as PowerPoint, not everyone has PowerPoint.