Apple has just released Mac OS X Lion Developer Preview 2 to members of the Mac Dev Program. You'll need to run a software update on the first preview of Lion to prepare for the update, reboot your system, then grab a download token from the Dev Center to use in the Mac App Store to get the 3.7 GB download to update. I know, that's a lot of steps, but you get a completely overhauled iCal UI and unified contacts window in iChat for your troubles, among other things.