Sorry if this is a bit off-topic, but I think it's related to your issue, albeit indirectly. With regards to maximizing limited shelf space (something I can relate to) -apart from trying to find slimmer cases- I've consolidated many of my movies into single multiple-disc cases (such as Kill Bill, Iron Man, Resident Evil, etc). In fact, I used the 6-disc LOTR theatrical case to put my LOTR extended films into, and simply stored the original box along with the additional dvd extras elsewhere.
At this point, I've gone as far as storing all my DVDs and HD-DVDs in modular album-type sleeve organizers, which happen to fit on my existing shelf nicely. If guests are curious about what titles are in my 'library', I have a nicely formatted HTML document they can scan through (exported from my movie library database), which also includes digital content stored on my PC.