This is something that of you have been waiting for a while now! Remote Server Administration Tools (RSAT) is essentially the WS08 version of the "Admin Pack". RSAT allows you to install many of the WS08 management tools on a Vista SP1 computer so you can remotely manage WS08 servers (full servers and server core). Some of the tools included in RSAT can also be used to manage WS03 servers as well.
More details about RSAT are pasted below.
Microsoft® Remote Server Administration Tools enables IT administrators to remotely manage roles and features in Windows Server® 2008 from a computer running Windows Vista with Service Pack 1. It includes support for remote management of computers running a Server Core or Full Server installation of Windows Server 2008. This feature has been requested by customers as a replacement for the Windows Server 2003 Administration Tools Pack.
To test the Remote Server Administration Tools Beta and obtain customer feedback, Microsoft offers a Feature Focus program for this update, starting November 28, 2007 on the Microsoft Connect site. By participating in the program, you have the opportunity to try the new Remote Server Administration Tools, and provide feedback directly to the product team. The download is available as part of the Windows Beta program