993 Carrera = 2 wheel drive
993 Carrera 4 = 4 wheel drive
Available in coupe and cabriolet - targa model came out in '95
272HP in '93 and '94, 285HP from '95
993 Carrera 4S = 4 wheel drive, with turbo body, factory lowered suspension, turbo brakes, 18" wheels, etc - came out in '95
993 Carrera S = similar to the 4S but 2 wheel drive (options slightly different though, different body) - came out in '96 (
AFAIK)
Both 285HP
993 Carrera RS - stripped down, fewer options, 300HP - '95, and in the US only - also came in RSR and Clubsport (both super lightweight, 3.8L, 380HP)
993 Carrera Turbo = 4 wheel drive, wide body, 408HP, two turbochargers, upgraded brakes, as seen in the 'kills bugs fast' ad - Turbo S available in '97 only (424HP)
993 GT1 = 600HP supercars - not street legal, except for the 'Strassenversion' (street version) - 30 were made, with HP reduced to 'only' 544HP. If you can find/afford one, I'm jealous
993 GT2 = 2 wheel drive, 430HP, upgraded brakes, wide body, etc. - *very* nice - came out in '96
This page is pretty helpful, although by no means exhaustive:
http://www.dennigcars.com/Pages/911_(993)_models_en.htm
and this is pretty good too:
http://www.flat-6.net/huge_list.php
Hope this helps!