Skype has just announced an update for Skype for Mac OS X, bringing better support for OS X Lion and bug fixes, as well as introducing HD calling.
From the official Skype blog:
With Skype 5.3 for Mac OS X, you’ll also be able to send and receive HD quality video when talking to your friends and family. You’ll need to use the Mac’s built-in webcam or choose from a variety of webcams from our Skype Shop, such as the Logitech C910, to make video calls in crystal clear HD quality. To receive clear HD video calls on your Mac, we recommend an upload/download speed of 1.5Mbps.
Previous versions of Skype already seem to run well on Lion, but official support should continue to address any bugs that were initially present when running Skype on Lion. The update is available for OS X 10.5 Leopard or later, and you can download it here.