Instructables.com has a really cool hack that involves putting your MacBook in a rack and attaching it to the back of your computer monitor. While this wouldn't work for me since I have two Dell monitors that rotate 360* and therefore have an arm in the way, it is a good idea. I also don't think it would work well with my Dell Latitude D820 because it seems a little heavy for the wire rack, but it would be cool to see if I could configure it to work with my port replicator!
I prefer a clean / minimalist looking desk and this hack seems to fit that model pretty well. Check out the article here.