Earlier today we published a whitepaper and set of sample scripts that walksthrough how to build a Silverlight "Direct Install" Experience on your own site.  You can download them for free here.  You can learn even more about it on Tim Sneath's blog here.

The whitepaper and sample scripts demonstrate both how to enable the direct install experience, as well as how to design the HTML UI of the site so that you can easily encourage end users to naturally click the install link.