You can make your evaluation in powerpoint, including videos, extracts and clips and then save your work. You then open 'KEYNOTE' on the macs and use it to open your powerpoint. You need to work in a quiet space and you basically present your ppt, including talking and it will be recorded (by the built in mics on the mac). This can be saved and exported as a film ready for uploading to your blog.
Here's a video showing HOW to do it and a video showing it having been done!
And it being done...
