I am a fan of Balsamiq. Balsamiq gives you a lot of design opportunities for application mockups of various kind. And I like the rough draft appearance to show it’s a draft of an idea. Not the final UX/UI solution. It shows the business actions within each item of the application. And the toolset is easy enough to use in a rapid mockup scenario with customers during discovery sessions.
Recently, I needed something fast and free.
I found Pencil. The Pencil Project is an open source toolset that creates wireframe mockups of applications such as desktop, tablet, mobile, and browser. There are some free Google based templates you can bolt onto your toolset. Also, it has additional features as mind mapping, application flow, and note sections in the diagram.
I highly recommend it as a supplement to Balsamiq especially if you do not have software budget.
Here is the official website: http://pencil.evolus.vn/
~ Tony Maddin ~