I record lecture notes, and they contain giant pauses filled with white noise. Is there some way I can get rid of those passages completely? Using Audacity, I can reduce the white noise (i.e. turn it into silence), but what I'd like to do is crop those bits out from the file so I don't have to play "hunt for the lecture".
Try this, assuming you can use a sufficiently recent (post 2007, unstable) version of audacity.
Summary of the suggestion, as requested by @slhck:
The effect is described here