As someone who has done a number of these things I have a few suggestions:

- Camtasia works well for quickies but it does not render the details of screen capture very well at small resolutions. One former employer has resolved this building a flash version of their interface just for demos- it looks just like the real thing but it is vector graphics so it can be changed without losing resolution. Time-consuming but they can also easily change branding for private-labeling the demo- good for business development.

- If you record your own voiceover leave spaces between all sentences and make sure you leave a moment of silence after each one. This makes it a lot easier to edit the V/O. Don't talk fast, talk a little dumb. Any audio editing software can slow or speed up your delivery.

- That being said, take your version, go to a V/O talent and get them to read it. You'll pay for an hour or two of their time and studio time. They'll send you a disc with files already clipped into pieces. Good talent makes a huge difference in both time saved and quality. They don't have to be local- there are services online that will take your script and turn it around fast.

- Keep it concise. Break up demos by 'problem-solved'. Don't solve multiple problems in one long demo. It's a demo, not a training flick.

- Put them on Youtube with your URL. There is no reason not to and YouTube is a de facto format for sharing video- everyone can use it.

One thing I found really useful is a book called The Art of Power by Thich Nhat Hanh, which is a semi-business related book about mindfulness. Listening to yourself is sometimes a hard thing to do. He offers a simple means of reconnecting.

Omnigraffle- there might be a trial version in there already. incredibly useful for designing/organizing ideas