Microsoft's 'SetTop' Vision
Unlike many other Web tablets, Mira actually doesn't function as an independent computer. Instead, it effectively relays data and commands back and forth from a PC via an 802.11 wireless network and Windows CE.Net, the latest version of CE. Letting the PC do most of the heavy lifting saves on battery life.
With an expected cost of $500-$800, I'm not sure how successful they will become... especially when laptops can be had for not much more.