Here's a consolidated list for the Hyatt, Marriott and InterContinental. Every code below is confirmed to work as of today. I have them more or less in order of what has worked best for me.
<b>Hyatt</b>
GE NC16700
GE International 13307
IBM 13717
Li & Fung 90010
Samsung 57039
Credit Suisse 12624
AAA 17500
AAA 15985
Credit Lyonnais 13516
Duty Free Shoppers N V 12114
Costco 13365
Bank Atlantic 79103
Senior Citizen 17497
Daimler Benz 99800
Company TVL Rate 68083
Company TVL Rate 23079
<b>InterContinental</b>
GE 000102806
IBM 000243132
Siemens 000104256
Ford 000103772
Federal Express 000109207
Travel Consultant IVTCD
Ace Hardware 100862437
<b>Marriott</b>
General Electric GEE
IBM IBM
Ford FRD
General Motors GMC
Accenture ACC
Siemens SIE
AT&T ATT
Pepsi PEP
A few general comments:
1. GE works the best just about anywhere followed by IBM, but sometimes the Siemens and Samsung rates will amaze you. I just got 70% off at the Grand Hyatt in HK with Samsung for example.
2. I have used these probably 40 times in 10 countries and I get asked for ID 50% of the time. I have a stack of business cards I printed myself and they have worked 100% of the time. Never had a problem, even at times when I thought I may. For example, I have stayed at hotels where I got an exceptional discount to find out it was because the office was right next door (Intercontinental Beijing / IBM) and my self printed cards were not questioned.
3. I don't know about others experience, but I get upgraded 25% of the time using these codes and being "with" these corporations. I still laugh when I hear, "Sir, since you with company X I upgraded you to a suite". My best ever was a two-room suite for $81 a night (IBM discount).
4. On a personal note, this ethical debate is total crap. These hotels are obviously making money at these rates, and why should an executive of a multi-billion dollar corporation get a discount and then an individual pays more? You're leveling the playing field. If you still feel bad, read this:
http://en.wikipedia.org/wiki/The_Hyatt_100