Memory usage in your ASP.NET app

At the PDC I saw a presentation where some optimization tips on memory usage in ASP.NET pages were given. The performance monitor was used to look at Gen 0, Gen 1 en Gen 2 usage of the garbage collector. The example was using a StringBuilder class to combine data and write this out versus using direct writes using Response.Write (which was much faster and consumes less memory). I am wondering if there are any good tools to look at memory consumption and garbage collection on a high-load website... Anyone?