Google recently announced that they are changing the service’s name here in the UK due to a trademark dispute. From today, all new invites sent to people in the UK will be for @googlemail.com (rather than @gmail.com) addresses. Nothing changes (so far) for existing users.
The Gmail logo.
The new Google Mail logo.
Why is this happening? The dispute with gmail.co.uk has been rumbling away for a while, and this seems to be the result. Google are still contesting their right to use the Gmail name in the UK, only now it’s being done in court.