Today I've published version 1.5 of Lemon on my web site for Download.
Lemon is a Java-based application with a graphical user interface that allows for comparing two LEGO® models that are stored in LDraw or LDD format; the common parts are listed as well as the ones that are contained in one of the models only.
It's also possible to check a model against the NXT Retail Kit or (new to 1.5) against the NXT Education Kit - comes in handy if you want to know whether a model can be built with one of these kits.
Moreover, the new version supports multi module models now and contains numerous bugfixes.
Give it a try, please, and provide feedback and proposals.
Addendum: If someone is encountering problems with Lemon, please do not hesitate to contact me via the contact page on my web site.