total recorder is a really simple program that records any audio going thru your sound card. you can record and save anything, as pretty much any kind of a file you like.
http://www.highcriteria.com/
I like to use cool edit for multitrack recordings.
http://www.oldapps.com/CoolEdit.php
I have a stereo 1/4"-to-rca, and an rca-to-1/8" stereo, that I have going from my guitar amp to my computer's sound card. it makes perfectly suitable demo recordings.