Mockup / Wireframe / Prototype Tools

Balsamiq “Mockups”

Pencil

Gliffy

  • free basic web functionality
  • $$ubscription model for featured version

SketchFlow is apparently coming back to VS2012 – Microsoft seems to be in a bit of a tizzy buttoning down all the loose ends in the latest transition to all things immersive.
Infragistics has Indigo Studio
There’s tons more out there… prototyping is apparently a very hot item