Apple previously updated its Migration Assistant app for compatibility between Lion and Snow Leopard, and now here's the original Leopard update. The Migration Assistant Update for Mac OS X Leopard smooths out the transfer from a Leopard Mac to one running with the newest Lion OS, making sure your data, settings, and apps all make the trip over.
Yes, it's not exactly groundbreaking. But if you've got a Leopard Mac sitting around and have been planning on picking up a new one complete with a Lion install, this will definitely be helpful in the transition. The update is of course free, and can be picked up from Apple's site.