QLab - it's free, and it is great.
I am going to lock this thread - as it is more of a sound design question than related to Stage Management - and there are other more appropriate places on the web for this sort of question.
--Further Explanation-- TotT has the potential to stray miles out of the Stage Management arena, and I want to avoid that - this post is basically my line in the sand - whilst SM's are often oping Sound, actually designing and creating playlists is a sound design question and is more appropriate for back stage 'techie' boards.