In addition to Snoop, Mole and VS2K8 is use:
- The Expression Blend 2.5 Preview
- Kaxaml
I'm in Blend at least as much as Visual Studio when I'm working on the UI in WPF projects. I use Blend to create the initial versions of a UI and then I'll tweak the xaml manually inside of VS. I use Kaxaml to "try things out". If I want to experiment and I don't want the overhead of creating a new project in VS or Blend, I'll use Kaxaml instead.