I've used this tip to share a single Applications folder with two copies of Mac OS X on the same computer (Tiger Developer Preview and 10.3). Enjoy!
[robg adds: I haven't tested this one, and I'm not sure if this is the best way to do this or not -- but I do get asked about moving Applications relatively frequently, and this seems like a simple solution. An earlier hint (much earlier, from 2002) had a much more complex workaround, and it seems like overkill for the task of just moving Applications.]

