I found the some topic on10, i think its very interesting for developers, The Microsoft Sync Framework is the platform that allows for taking web services and databases offline. It also provides optimized P2P sync for any sort of file, like music, videos, photos, contacts, or settings. With the Sync Framework, developers can add sync support to their applications, services, and devices in order to enable collaboration and offline capabilities. If that's something you're into, you can download the test build of the Sync Framework now and check it out. The Community Technology Preview (CTP) 2 test build of the Microsoft Sync Framework was made available on the
Downloads site on the first day of MIX08. You can also watch a video to see a demo and walkthrough of the key components involved in building an app using Sync.
The Sync Framework works on Windows Vista, Windows XP, Windows Server 2003 and Windows 2000 Service Pack 3. 
For an example of what Sync can do, check out SyncToy 2.0 Beta. SyncToy is a free tool which helps you copy, move, rename, and delete files between folders and computers quickly.
Enjoy and happy coding :)