I knew a guy that used his pocket pc and 1 gig microdrive to record certain parts of his lectures then transfer them to his desktop adn make then wma fiels so they are smaller and put some back on the pocket pc for later.
It depends on the sound quality of the room and where you are in comparison to the speaker but you can definatly do something like that.
There is a program called Resco SPA (Speech Personal Assistant) that lets you have more control:
Resco SPA