For audio recording and editing, I really like Cool Edit Pro.
As for composition, I would recommend Sonar 3 PE. It comes with many nice plug-ins including the wonderful Lexicon Pantheon reverb plugin.
For DXi plug-in instruments, Edirol has a nice line of inexpensive products.
For scoring and printing, Finale 2003.
There are many others out there, but these are what I'm stuck on now...