While I had been not interested in such functionality I successfully forgot about it. But today I remember about because I was need some tool to making mockups and get a big problem which consists in a very few good and working solutions also being free to use without harmful prices.
Most popular applications ( like Wireframe Scatcher for Eclipse) is good enough and I'd probably decides to start use one of them, but this is the problem: their or very expensive (as for me, of course) means starts from 60$ or in beta-stage.
I have googling for good one for a long time and, of course, I have found what I looking! It's - MockFlow.
MockFlow is Flash-based and available from web interface as flash application and from desktop as AIR-application ( you need AIR Player from Adobe ). It has rich components collection, collaborations features includes chat, many complex components such like ready chat or web-sites mockups and many other sweet thigs.
It's totally free with some limitation for use or 40$ for 1 year of usage.
Any way you must try it: http://app.mockflow.com/mockflow/
