This could work. Buy one of those suction cup phone microphones (RadioShack?) and plug it into your computer's mike input jack.
In OS 9 you can use the Sound control panel to record the sound (I believe), in OS X you'll need a third party application. Save as a QT movie.
Enjoy the memories.
EDIT:: Just thinking...isn't there some software that'll act as a phone? Dial, talk, etc. maybe even record?
[ 04-22-2003, 12:11 PM: Message edited by: kps ]