Interaction design software is only recently becoming one of the heavier markets for new kinds of SaaS and new markets for browser based cloud solutions. With the very visual mindset of modern designers (understandably), and with designing software becoming an increasingly intricate field, especially with SaaS and the lift of some standardization, it’s understandable it’s taking off. But, what kind of interaction design software is available out there? Well, it depends on what you need. Do you want to go SaaS, or do you want to use a more traditional solution? I’ll point out three solutions that work, but between you and me, I think the only particularly effective tools are those in IDEs. External prototyping tools, it seems to me, tend to be in the way more than anything. But, do as I say not as I do, and you absolutely –should- be using something for this. #1 – Microsoft Visio I’ve used Visio off and on since before the SaaS boom, when it was another big Office component, and not something capable of running over browsers at all. This solution is more about diagramming, but it can also be used to draft floor plans, or to work out prototype navigation flows and interface prototypes as well. It’s very easy to use, with a point and click “drag around and scale” type of interface, and the visual elements are expandable to make new kinds of diagrams including UX-specific fields and even circuitry and chip design as well. #2 – Balsamiq Balsamiq is more about specifically creating mockups of interface concepts, and it does this very well. Once you’ve mapped out your interaction, you’ll want to build your mockups based on various states of this, within something like Balsamiq. It’s easy to use, like Visio, and mimics the experience of using an IDE’s interface design very closely. I’m not wild about the “wobbly line” aesthetic of the representations of the controls, but that’s a minor complaint at best, really. A lot of my colleagues use Balsamiq, and while in projects I’ve been involved in, we used the IDE for this aspect, it’s recommended that you don’t do that. So, I recommend this one for this aspect. #3 – Gliffy This is an alternative to Visio, if you’re not a fan of Microsoft, or simply don’t want to pay the absurd prices Microsoft charges. It’s on par with Visio in most respects, though it’s not quite as powerful, attractive and diverse. Still, it supports navigation and flow charting, mockup creation, technical designs and floor plans, so it’s basically a cheap alternative to Visio. So, what I recommend is that you adopt something like Visio or Gliffy as your sketching and charting tools (as I’m not as big a fan of paper prototyping as some), and then using something like Balsamiq to actually mock up the layouts and stages of the interface during any point in the charted interaction. These are your top choices for interaction design software right now, but there are a lot of other choices out there. So, do your research before you settle on any choices here. This is just to give you an idea of some of the better stuff, not to show you all there is.