If you are using the Silverlight 2 MediaPlayer that comes with Expression Encoder but are not using IIS Smooth Streaming, you can slim the player down from 162k to 90k pretty easily.

First off, edit a copy of the template you want to put on a diet in Visual Studio:

Next, open the Expression Player project and remove the reference to adaptive streaming:

Now comment out the adaptive streaming references in Expression Media Player:

Using directive:

OnMediaOpened:

AdaptiveStreamingSourceFactory class definition:

SourceFactory initialization in the constructor:

If you now recompile the project and try it out in Expression Encoder, you'll see that the XAP has shrunk:

Part two of this tip can be applied to any XAP made in Visual Studio 2008 or Expression Blend. 

1) Rename the XAP to ZIP and extract the contents using your favorite ZIP utility.. here I'm showing how to do this using the shell:

Now recompress it using the same tool and you'll see a magic saving of a further 22k:

For an even greater saving, it would be possible to eliminate the dependency on LINQ but, for now, I shall leave this as an exercise for the reader :-)