Recently I tried Balsamiq Mockups for my wireframe design, it is a really really wonderful tool for sketching your design ideas.
Here are some thoughts:
1. Why I use Balsamiq Mockups?
I’m a UI designer specializing in software user interface design.
I tried lots of tools, like Axure, Mockbird, and etc.. When I came across Balsamiq Mockups, I found that this tool is easy to use, and the more important is that it saves me lots of time.
Balsamiq Mockups provides a bunch of elements that I probably use in the UI design.
2. What benefits I got from using Balsamiq Mockups?
Since Balsamiq Mockups uses hand writing and hand drawing styles, it leads the me focusing on the main work flows or main structure of a design without considering others.
Balsamiq Mockups makes me feel that I’m drawing, but it implements more things than drawing. It’s quick enough for me to sketching my ideas.
Good:
Balsamiq Mockups is a cross platform tool. I can use it on Windows, MacOS, or even other systems.
It is faster than my drawing with pencil. 
Bad:
I cannot do interaction designs.
How to get Balsamiq Mockups:
Visit their official website: http://www.balsamiq.com/
Installation:
If you don’t have Adobe AIR installed, you have to install Adobe AIR first.
Then you can install Balsamiq Mockups.
Enjoy! :]
