A fast and smart tool to perform wireframing is indeed Balsamiq which is very smooth and easy to use, which feels like drawing on a whiteboard which is the computer screen.
It has a variety of features, like:
- The wireframing tool is so fast that you can keep experimenting with your ideas and keep generating beautiful graphics.
- Build your own user interface with options that you use the most.
- Get a complete library for the UI skins. You can switch between one skin to the other, any time.
- The whole community can see your creations and you can get instant feedback and opinion.
- There is a clean UI skin also available which makes it easier to present the work.