Andreas Weidner wrote a great ULP for that. With it you can take any
component from any Eagle library and 'explode' it, meaning that the
schematic symbol will be transformed into just lines on a documentation
layer and the PCB package will be removed. So you can add the parts that
are not on the board which makes reading the schematic a lot easier.
You can find the ULP from the 'downloads' section on the Cadsoft website.
