Here are ALL the English-language (domestic) audio mixes for Star Wars:

Theatrical (1977) Mixes:
- 1.0 Mono (1977 35mm Theatrical and some early-1980s TV broadcasts ONLY)
- 2.0 Stereo (1977, 1981 35mm Theatrical, early laserdiscs)
- 4.2 Six-Track (1977 70mm Theatrical ONLY)
Home Video (Pre-SE) Mixes:
- 1985 2.0 Stereo (remixed by Ben Burtt; included on early 1990s VHS tapes and mid- to late-80s laserdiscs, including Japanese Special Collection)
- 1993 2.0 Stereo (downmix of the 4.2 six-track with newly-added sound effects; included on 1993 Definitive Colleciton/1995 'Faces' laserdiscs, 'Faces' VHS, and 2006 Trilogy 'Bonus Discs')
SE Mixes
- 1997 5.1 Surround (theatrical SE mix, included on Japanese laserdiscs)
- 2004 5.1 Surround (SE DVD mix, with many technical problems - also included on Disc 1 of 2006 DVDs)

There. If I've gotten anything wrong, let me know, but I think that's it. I have the 1977 mono, 1977 stereo, and 1993 stereo in WAV format synched to the GOUT discs, and the 1985 stereo that hasn't been synched to anything yet.

What I can't get a good answer for is whether or not Empire and Jedi were remixed in 1985 (I know Empire was in 1993, since there's a sound effect missing in the 1993 mix), or if Jedi was in 1993. And if the 1983/1985 mixes, if they exist, are available anywhere for Jedi (it's been deduced where the 1980 Empire mix would have to be if it's different from the 1985).

--edit--

Just noticed I posted pretty much exactly what Hairy Hen did. Sorry about that - I've been battling a pretty bad cold for the past couple days, I'm not as observant as I should be.