Regards my recent trip to Germany (with resultant podcast) to present about CMT and Security, I lucked out when I did the actual presentation:
Literally as I stood to present, in the hope of getting an audio recording I plunked my dinky, go-everywhere Canon IXUS 900 on the table and left it recording video at 320×240; I lined it up with the screen so it could watch the slide changes and the camera sat happily on the table for the entire talk.
In post production I realised the result was good enough to use as a presentation video; so I enlarged it 2x using QuickTime Pro, imported it into Final Cut Express, normalised the audio, and spliced the slide graphics over the video. This was less complex than it sounds, except for the learning curve.
The result is here:
Duration: 16 minutes-ish.
Please note: this is a presentation written for an English-speaking German audience. Please adjust your expectations accordingly, eg: the appropriate shape for beer glasses in a given culture
 Method: Export Keynote for PDF, present PDF; use MacOS Automator to 1) save PDF pages to individual images and 2) crop images to same size/aspect ratio as the video footage. Import images into FCX and drop them onto video.