I first heard of virtual appliances a couple of years ago during a trip to Sweden to hear about Intel's AMT technology. I didn't hear about them from Intel, but from Gartner analyst Brian Gammage, who reckoned there was a gap in the market here with a window of opportunity spanningn several years before Microsoft got his act together.

I reckon he was right - and no, this isn't a case of hindsight. When VMWare ran a competition this year to create virtual appliances, it got several hundred appliances entered. You can, for instance, download a complete stack for the Asterisk IPPBX - Linux, Apache, PHP, MySQL, Asterisk itself - all fully confiugured and ready to go. How cool is that? Sure, these things are still a way from mass take-up, but some companies - vendors at least - are beginning to use them in anger.

I was having lunch with Paul Di Leo, the CEO of Zeus Technology, a couple of weeks ago, and he is very excited about the potential of virtual appliances. They will, for instance, allow Zeus to distribute fully working stacks of trial software - you want to try out their extensible traffic manager? Download the appliance. You don't need to install software in the traditional sense of the word, simply download it into a VMWare Player.

I gather that Zeus is also starting to use virtual appliances in production environments in housem, where it effectively has anm application sitting on a dedicated virtual OS that can move around, and is never materially affected by any other apps. There are some great possibilities here, not least for security - imaging firing up a browser on a dedicated OS. The OS layer starts to look much less signficant doesn't it?