Milkytracker + Audacity + jamin
I just master and mix tunes, but I work in Linux so choices are a bit limited.
That said, audiacity (1.3.7 beta) and jamin are a GREAT combo. Jamin is a nice mastering tool and by far the best thing I've found available for *nix. Audacity does pretty much everything I want it to and the 1.3x versions are SO much better than the stable line.
http://jamin.sourceforge.net/en/about.html
For replayers, I use dumb (IT, S3M), milkytracker (XM, sometimes MOD and S3M), uade2 (weird amiga shit), sidplay2 (SID, of course), bassmod (XM), ayemul (speccy tunes), asap (Atari-8 tunes), adplug (Adlib), sc68 (atari-16). Sometimes I use deliplayer or winJAM under wine emulation.
Some of my tune conversions can be found here: http://www.esnips.com/web/demoscenetunes