You’ve probably read this already elsewhere (it was hard to miss!) but here you go anyway:
The next generation of Windows for desktops and servers have been released as public betas. Windows 7 is the successor to Windows Vista. You can download it from here. Windows Vista may not have had the features to make you want to upgrade from XP but Windows 7 might just have them. The really cools ones are when Windows 7 is teamed with Windows Server 2008 R2. These include BranchCache and and DirectAccess. By the way, contrary to rumours spread by the uninformed, Windows 7 is not a new version of Windows XP. It is an evolution of Windows Vista. If your software and devices work on Vista they should work on Windows 7.
Windows Server 2008 R2 brings some new stuff and can be viewed as Windows Server 2008 V1.1. Mark Russinovich talked about the new features of power savings and virtualisation at TechEd EMEA. There are evolutionary improvements all around including web services, virtualisation (Hyper-V will have live migration AKA VMotion thanks to a new cluster file system), power savings and new remote access and branch office/remote computing access. You can download the beta now.
By the way, these betas are very popular right now so the links are being hammered. Downloads might be slow for a few days.