For lightweight storyboarding I use Lucidchart (they have a set of iOS-specific icons and such which save a little time, but nothing fancy). For full-color clic

For lightweight storyboarding I use Lucidchart (they have a set of iOS-specific icons and such which save a little time, but nothing fancy). For full-color clickable demos I've had a lot of fun with invisionapp.com That being said, several clients of mine have preferred balsamiq.com, I'm not sure why exactly, they just found it easier to use.