...can be found here.
http://www.3drealms.com/cheat/shadowwarrior.html
http://www.3drealms.com/sw/secrets.html
http://www.3drealms.com/sw/walkthroughs.html
Or if you'd like all this stuff offline I've put together a zip file here:
http://www.mediafire.com/?y9b9rstavaq134h

This is just for the base game for now. I'll put together something for the expansions if anyone would like.

Wanton Destruction walkthrough and all secrets (by Francesco Poli):
http://pastebin.com/Qwt8QaDN
NOTE: The final boss does not spawn when playing the first 2 difficulties of Wanton Destruction, making it impossible to finish the game.*

Twin Dragon Video Walkthrough with all secrets (by galleyuk and PekingDuck):
http://www.youtube.com/playlist?list=PLEA0D488ABC92959A
Check each video's description to skip right to the secret you need.
The first secret in level 5 of Twin Dragon cannot be acquired unless playing on the 3rd or 4th difficulty setting. This is due to a mine hidden behind the wall not spawning.*

* - I've fixed the issues, you can find the new files and instructions here:
http://www.gog.com/forum/shadow_warrior_complete/wanton_destruction_fix

yes please

I can't find the original Wanton Destruction walkthrough anymore so I put it up on pastebin:
http://pastebin.com/Qwt8QaDN
I can't confirm this, but take note that even with cheating, you cannot finish Wanton Destruction on the first 2 difficulties.

I hope those Sauce Ports guys or some extreme pro modder fix those damn bugs.

Not likely, they would need the source code to fix the problem.
You have to remember that the two SW add ons were never officially released. 3d Realms, rather then do the add on themselves,sold the licence for the add ons to two different companies. When Shadow Warrior did not sell very well,the two companies decided not to release them. Both were released as a freebie downloadable in the early 2000's.

Not quite. Twin Dragon was released in 1998, Wanton Destruction in 2005.

The link to the combined SHadow Warror walkthru is not working.

Sorry about that, updated the link.
http://www.mediafire.com/?y9b9rstavaq134h

I always liked to use the bunny rabbit rocket cheat, heh

With Twin Dragon from which level do you access to the secret level?

Level 11, the Fortress.