Wow, quite a few responses ...

NJDavid ~ You're probably right, posting the codes publicly might not be a good idea in some cases.

What I'd really like to find is some way to get discounted hotel rooms at Hyatt or Marriott or another chain. I work with one company that has negotiated rates with Hyatt, and they always seem to be able to get a pretty good deal at Hyatt. It seems to me that if I could get one of these discount numbers, even though it might technically be against the rules, it would benefit the company whose number it is in the end anyway since they would get credit for my stays. If I was ever asked for an ID at the hotel, I could always play dumb and say I left it in my car at home or something.

For car rental I probably wouldn't want to mess around with, because of the whole CDW thing as you mentioned.