https://moqups.com/ « a wonderful HTML5 tool.
Any particular reason you like it more then myBalsamiq etc?
I like that it is a web app and not Flash! Very easy to use and fast. And free (but I would happily pay).
Yeah, this is the most simple, beautiful mockup tools I saw over the years.
Falls into a similar bucket as Fireworks, but I primarily use Illustrator for mockups.
I've been using http://uxpin.com/, it even handles responsive breakpoints.
iRise is a high end package that is quite good: http://www.irise.com/
Edit Room: http://www.edit-room.com/ (my product) Only one that does full responsive design with custom breakpoints and all flexible units for the CSS it generates.
Hey Kevin, feel free to add it as a Viewpoint if you like :)
Not a dedicated tool but LOTS of people using Keynote for mockups these days.
I never understood this, there are so many awesome and free online tools that do a great job. Keynote seems a little clunky for this.