Quite some time ago, I wrote small utility which helped to create external map manifest file for Silverlight assemblies. This manifest is needed to enable XAP reduction feature (you can read more about it here).
I have been told, that the utility is not working with assemblies compiled with Silverlight 5, so I decided to update it. The new version compatible with Silverlight 3, 4 & 5 assemblies.
Please note, that new version requires .NET 4.0 Client profile in order to work.
Updated version can be downloaded from here.