All new Finder, with iTunes-like interface
New file and window management tools
On-the-fly user switching (like WinXP's but flashier)
New iChat with VoIP and Video features
New Mail app.
IPsec-based VPN for Microsoft and Cisco networks
Local file encryption, called File Vault
Built-in Fax capability
Windows interoperability enhancements
New Preview app with much better PDF handling
Advanced font management
And the bad news...an "end of the year" release date.
However, version 1.0 of Safari is available now.