Here are some links to help you as you begin planning to deploy Hyper-V:

Hyper-V Release Notes

Hyper-V Planning and Deployment Guide

Hyper-V RAM Calculator Spreadsheet

Webcast: Virtualization Capabilities of Windows Server 2008 (Level 100)

Hyper-V: Hardware Considerations

Hyper-V Solution Accelerators: Infrastructure Planning and Design -Windows Server Virtualization

Dell Solutions Guides for Microsoft Hyper-V

Planning for Hyper-V Security

Security in a Virtual World Whitepaper

Hyper-V: Planning for Backup

MSDN & TechNet Powered by Hyper-V Whitepaper