Leopard is the code name for 10.5 which has just been generally
released (not beta).
Here is what I have found out about it.
Leopard is version 10.5 of Apple's OS X operating system for the
MacIntosh. Most changes are to the look of the desktop. You have
stacks — icons that pop open displaying their contents in a fan (or
optionally the traditional grid). The active window has a drop shadow.
Cover-Flow while browsing folders lets you see a preview of the
document. It can search all machines on a local LAN. It has
Magellan-like Quick-Look to let you rapidly view files without loading
the full application. Time Machine is an incremental backup of your
entire machine that backs up any changes every hour to on external
hard disk. It lets you support multiple desktops that Apple calls
spaces. You can move apps between spaces in the bird's eye view.
Unfortunately, it does not support Java 1.6.