I've not had a chance to download it yet, but SQL Express Manager (XM) [1] for SQL Express is now available. You'll need the newer SQL Express bits [0] to install XM.
End of line.
[0] SQL Express bits – http://www.microsoft.com/downloads/details.aspx?FamilyId=66120BE8-826A-482A-8264-B1836F28FD79&displaylang=en
[1] SQL Express Manager bits – http://www.microsoft.com/downloads/details.aspx?familyid=8f92556a-6c3b-47d2-9929-ecdc5a4d25ae&displaylang=en