Really the only chain that I have found to have a blanket corporate code that can honestly be used by anyone (instead of IBM's code, or my company's code, etc) is Hilton.
0560041604 works at Hampton Inn, Doubletree, and Embassy Suites.
N0041604 works at Hilton, Hilton Garden Inn, and select Hilton Grand Vacations locations.
I have randomly found discounts or corporate codes for other chains just be searching. FlyerTalk is a great resource that a PP mentioned. But they really are few and far between. I have used other corporate codes at Marriott because the code is the same at all hotels. Hilton changes theirs for each hotel and each company. My company had a very specific code for our Doubletree hotel in New Jersey near my last client, and that code was specific to that hotel and could not be used at other Doubletrees.
ETA: 'Liking' the hotel chains (like specifically Hyatt Place) can sometimes lead to discounts. Certain properties sometimes offer discounts through facebook or twitter.