What exactly are you trying to do with the audio?
For producing some basic simple programs are fruity loops and acid 4
For producing more complex stuff some popular programs are sonar, reason and logic and protools.
For single track editing (cutting out stuff, EQ's, mastering) soundforge is the most popular. Also a good recording program.
Adobe Audition (Cool Edit Pro) is a good combonation product. Handles recording and single track editing. I am not feeling it's production capability's though.
And another program is Ableton Live. It's live software for Live PA and meant for DJ's who want to get REALLY creative. You need a good DJ mixer designed for MIDI which are over 1G to really use it. For 150$ you MAY be able to aqquire a device that generates Midi.
And if you want to mix tracks like a DJ (like me) you really need DJ eq uipment and not a computer program.