You can convert (reconstruct?) your PowerPoint in a simple video program like
Windows Movie Maker, save it in a video file format, and upload it to your blog.
PowerPoint allows you to 'save' your slides as JPG files, these can be imported into Windows Movie Maker. You can also import the audio files that were included in the Power Point presentation... the result is an equivalent video.
Alternatively, I uploaded the PowerPoint presentation to Slide Share, an online media sharing resource specializing in slide show sharing. Note: The audio does not seem to carry into the viewer.
Scribd, too, allows PP upload...
Also - there are a number of useful YouTube videos on turning PowerPoint into video, here's one that appears to be useful.... http://www.youtube.com/watch?v=xZmOVt_BIAE