i just got a new laptop and probably will be my main keep for the next 3 years. I am looking for suggestions for software needed for a productive silverlight developer. In addition to the basics Visual Studio, Blend and the SDK.
With the exception of SketchFlow, I would say the following:
If you're truly trying to be a productive developer, don't install anything else. That way, you won't be tempted to leave 'the zone'.
If you want to do data-driven apps, you may be interested in RIA Services.
I would start with everything from the Get Started site.
Kaxaml is always fun to play with, although a bit outdated, and free. This comes with some nice templates that can be a great learning tool.
Recently I've really been enjoying Silverlight Spy (not free, but there is a trial)
Fiddler (or another proxy) is a must have for monitoring traffic from your Silverlight application. Check out this post for monitoring localhost traffic.
Additionally, you might want to take a look at the Composite Application Guidance (aka Prism) library. This is not something you install, but is great guidance for building Silverlight (and WPF) applications.
In addition to the set of tools you've started with I would add:-
+1 for Kaxaml - I use it quite frequently to get color values, test the widths of things, and other XAML miscellany. It's a lot more light weight than Blend and I am more frequently than not editing XAML in the code editor of Visual Studio.
I don't know if this is the right forum to prove this hypothesis but I think most Silverlight developers edit their XAML in Visual Studio, not Blend which is why having a light weight alternative is handy some of the time.
You will need Blend, however, it has no equal for editing control templates / styles.