One of the great things about KDE is that it makes heavy use of DCOP.
The only Linux command you need to know is apropos (pronounced app pro po) Yes, it rhymes.
mp3split is an awesome command line utility to split long audio files using silence detection.
It takes some playing around with to get used to all the options, but it is extremely powerful.
Recently I volunteered to record video for the DrupalCamp Seattle 2008. It quickly dawned on me that to record 10 hours of video, bring it home and capture it to disk and then compress it would take 30+ hours. Also, that wouldn't be anywhere close to live and they were hoping to post the video as soon as possible. Since I am only running Linux on my laptops now, I decided to see what could be accomplished via command line tools in Linux. I quickly stumbled on ffmpeg and dvgrab. DVgrab can capture raw dv from firewire and has features for detecting scenes when capturing from tape.