Jamie Cool took the auto-updating technology out of Terrarium and made it into its own component solution for adding application updates to your app, which was pretty cool on its own... but now it is even cooler as PAG (the same MSFT group who brought you the Data Access Application Block, etc.) has taken Jamie's code and updated it with a whole host of new features including support for background copying using BITS. Check out the GotDotNet workspace if you want to look at the component(s) as they are now and look forward to a public release on MSDN some day soon.