I'm a big fan of InVision for clickable prototypes. You can string together static screens with hotspots that can look and feel like a mildly interactive site depending on the level of fidelity you're looking for. I've built many demos using this service. Clients respond well to the interface and developers understand what happens when you click different links. Let me know if you'd like to know more.
http://www.invisionapp.com/

As for quickly mocking up a video, you can hack together a quick version using Powerpoint (set timed transitions for slides) and add music or voice overs using iMovie.

Quicktime also has an out of the box screen recording option that can supplement the above options.

Above all, be sure you have use case defined in a script with linear flows articulated via screens.

Scott