Global Hotel Alliance (GHA) consists of more than 300 hotels under 14 different brands in 52 countries. The loyalty program of the GHA is called Discovery and it has three tiers (Gold/Platinum/Black).
EDIT (June 10): This offer has now expired. Sign up for out blog email newsletter to be notified when it becomes available again.
Now, you can sign up for the instant Platinum status that is valid until February, 2015.