We can start with music production software.
There are many types of software for this. You have
sequencers, which let you record multitrack projects. Most of the major ones today incorporate both audio and midi, whereas some still only support one or the other.
Some sequencers come with a lot of
software instruments and effects in the form of VST (Virtual Studio Technology) instruments, a technology developed by Steinberg and used by a wide variety of plugin developers today. Alternatives to VST are DirectX ("DX") plugins, Audio Units (for Mac OSX), RTAS (for the Pro Tools system).
The most popular sequencers are (and this is not a complete list):
Pro
Cubase SX (now in version 3). There is also an SL version which is much cheaper.
http://www.steinberg.de
Sonar 4 (Studio or Producer Edition)
http://www.cakewalk.com/Products/SONAR/default.asp
Pro Tools (expensive, requires certain hardware)
http://www.cakewalk.com/Products/SONAR/default.asp
Semi-pro (I'm not quite sure where to draw the line so I use convention here)
Ableton Live 4
http://www.ableton.com
FL Studio 5 (Possible the most affordable all-in-one solution)
http://www.flstudio.com/
All of the above come with just about everything you need to create, arrange, produce, and edit music.
Another option is
Reason 2.5 (soon 3.0. This is a complete "standalone workstation" which does not support VST but still comes with just about everything there is - very popular and is used on a lot of records)
http://www.propellerheads.se
Budget (may still be used for professional purposes)
Tracktion (this is a true bargain sequencer at $80 and has become very popular)
http://www.mackie.com/products/tracktion/
Energy-XT (Even cheaper but incredibly versatile - can also be used inside other hosts)
http://www.xt-hq.com/
For Linux (just found this the other day)
http://www.rosegardenmusic.com/
I own the following: Ableton Live, Reason, FL Studio, and Tracktion. I most ly use Ableton Live, which is an incredibly fun tool to use. Sadly it does not have a built-in audio editor.
For
audio editing there are a lot of options. Tinny mentioned Adobe Audition, which is excellent, but quite expensive.
Some alternatives are:
Audacity (Win/Mac/Linux) - FREE
http://audacity.sourceforge.net/
Goldwave (Windows) - used by many pros, actually
http://www.goldwave.com/
Wavelab - pro software from the makers of Cubase (there is an "essential" pack which is cheaper)
http://www.steinberg.de/
Okay, that's enough for now.