Some free stuff you can use in your UX design process
Classic Windows widgets Axure library
Library with old school MS Windows 95 / 98 UI controls and components that can be useful to create prototypes of some basic Windows desktop apps, such as service utilities or diagnostics tools.
Mac OS X widgets Axure library
Library with standard components of Mac OS X UI controls and components to prototype Mac OS X desktop applications
Heuristic evaluation checklist
Universal checklist to evaluate user interfaces with more than one hundred heuristics inside.