CRM 2011 just released today and you may download it on the Download Center.   There will be no in place upgrade from beta to RC at this moment.  You have two options at this moment.

Option 1: Backup your database, create a new RC environment, then import/upgrade the beta org into RC.

Option 2: Uninstall beta, reinstall it and using the connect to existing data base option.

You may download the bit here.

CRM 2011 Server RC

http://www.microsoft.com/downloads/details.aspx?FamilyID=c3f82c6f-c123-4e80-b9b2-ee422a16b91d

CRM 2011 Outlook Client

http://www.microsoft.com/downloads/details.aspx?FamilyID=22dc423a-7194-491e-a169-6ace16bfdd36

Language Pack

http://www.microsoft.com/downloads/details.aspx?FamilyID=db44c564-2338-407e-980a-c9c83ad37729

Email Router

http://www.microsoft.com/downloads/details.aspx?FamilyID=a995f6ad-0099-42fd-9b22-cf7b3d40a2bf

BIDS

http://www.microsoft.com/downloads/details.aspx?FamilyID=64a09b75-8376-4b9d-aea3-8a83a1837c4d

SharePoint Connector

http://www.microsoft.com/downloads/details.aspx?FamilyID=23c0f351-8694-4d92-9ddf-34a949aec6a7