Don't you just love PowerPoint? However, based on research when you have a presentation with slides and a voice you lose 55% of your audience (referenced from Present.me). Well, Present.me has created a product that is free ( but you have to pay if you need more than 10 minutes of recording).
Present.me is a web service that lets you create effective presentations through your PowerPoint files. What makes this site unique, is it lets you add a narrative to the presentation. Once you upload your PowerPoint, you can record a narrative through your webcam and microphone as if you were presenting the slideshow. The final presentation then appears with your webcam recording on the right and slides on the left. A filmstrip view of the slides is also given on the bottom of the presentation.
Click on this presentation to see a sample.