Outlook 2010 now allows multiple Exchange accounts per Outlook profiles. By default the limit is set to three, but from what I am reading you can increase it to 15! I have not tried it yet but here are the instructions:
You can make the change through Group Policy or the registry. The Group Policy setting is located at Administrative Templates, Microsoft Outlook 2010, Account Settings, Exchange. Double-click Set maximum number of Exchange accounts per profile and set the required number of accounts. You need to import the ADMX files onto the machine editing the group policy object before the settings are available.
To make this change in the registry, navigate to HKEY_CURRENT_– USER\Software\Policies\Microsoft\Exchange and set the DWORD value MaxNumExchange to the new limit (between 1 and 15).