I used Keynote (the Apple version of Powerpoint) to create the diagrams in the article. It's a step above a pencil and pad of paper but not so sophisticated that you'd need to be a rocket scientist to achieve the same results.
Here's a list of software you can use to prototype.
DESKTOP APPLICATIONS
AppCooker (Mac)
Axure RP 7 and RP7 Pro (Win)
Balsamiq Mockups (Win/Mac)
Briefs for Mac
Flinto and Flinto Lite (Mac)
ForeUI (Win/Mac)
Keynote (Mac)
Microsoft Powerpoint (Win/Mac)
Microsoft Visio (Win)
Omnigraffle and Omnigraffle Pro (Mac)
Pop Prototyper (Win/Mac)
Sketch (Mac)
Simulify (Win/Mac/Linux)
UX Toolbox (Win)
BROWSER-BASED APPLICATIONS
InVision
IRise
JustInMind
Lucid Chart
Marvel
Pixate
Proto.io
ProtoShare
Solidify
MOBILE APPLICATIONS
iMockups (IOS)
Keynote for IOS
Prott (IOS)
Last edited by Maria - Computer Careers; 02/12/16 09:46 PM.