For example, there is a song on Kylie's Light Years album - Password - which does not come up on the track listing. Seems a bit mean to have to buy it via iTunes when I already own it...

If you have the cd, simply use a program like Audacity to grab the track and cut it yourself.

Usually hidden tracks are at the end of the last track, when you put the CD in you may have all the tracks at roughly 4 minutes, but the last track is about 12, there's your hidden track