Video and Audio composition tools?

I would like to make some tutorials and load them on to YouTube for the benefit of other Synfire users, and I was wondering if anyone could recommend some free or cheap software that is easy to use for this task (using Windows 7)?

I downloaded Video Capture by Debut to try out, and although it's easy to use, I can't seem to record audio with it.  That may be because I'm using a Saffire Pro audio interface, rather than the built in computer speaker system, I'm not sure.

I want the ability to speak through my microphone whilst recording the audio output of Synfire at the same time, all through the Saffire interface if that's possible?

I don't want to spend a lot of money on something, as it's more for the benefit of other users than myself.  But I would like to give something back for all the help I've received on here.

Any suggestions?