Thanks to everyone at NxtGen Oxford who came to see my ASP.NET scalability presentation last night. The code and slides are available for you to download at http://www.philippursglove.com/ScalableASPNET. I haven't had chance yet to work out why the SqlCacheDependency demo didn't behave, I'll look at this later on today and update this blog entry when I've worked it out! Feel free to email me at email@example.com or comment here if there are things that need more explanation or you just want to discuss something.
Update: I just figured out why the aspnet_regsql command-line was failing when I tried to enable my Northwind database for caching. I hibernated my laptop when I left the office on Tuesday afternoon, on Tuesday evening when I switched it back on it couldn't contact our domain. So when I tried to run aspnet_regsql with the '-E' switch for integrated authentication, I couldn't be authenticated against our domain and consequently SQL Server's security (correctly) wouldn't let me do anything. If I'd instead used the '-U' and '-P' switches with an administrator username and password it would have worked.