Since July 19th 2012, all new sign-ups for Dynamics CRM Online have been switched over to the Microsoft online services environment which is the same subscription/billing platform used by Office 365 and many other services from Microsoft. Among many new things with this switch over, one significant technical change is that it allows CRM Online customers and partners to use the same identity platform as Office 365. This means that users of CRM Online & Office 365 will have the same set of username/password to access various services and it also helps administrators to manage their users in an effective way.
If you are a Dynamics CRM developer or partner developing with the CRM Online web services, you might want to update your code to support the new identity platform (now called as Windows Azure Active Directory - WAAD in short)
For .NET developers, this page on MSDN shows you all the details on updating your code: http://msdn.microsoft.com/en-us/library/hh670628. Also the downloadable SDK code samples have been updated to reflect the various authentication options.
For those that are writing code in platforms other than .NET, you might want to checkout the updated SOAP-only web services sample posted here: http://blogs.msdn.com/b/girishr/archive/2011/02/04/connecting-to-crm-online-2011-web-services-using-soap-requests-only.aspx
You can sign-up for a trial account in the new platform at http://crm.dynamics.com and manage your subscription at the Microsoft Online Services Portal – https://portal.microsoftonline.com. Existing users of CRM Online using Microsoft account (formerly Windows Live ID) will eventually be migrated to the new environment and the timelines for this migration is still TBD.