Removable storage. It's something you either depend on greatly on a daily basis for work or something you've never heard of or bothered using in the past. Nevertheless, allow me to explain one of these products I picked up not long ago and why I consider them one of the most useful PC products ever invented.
Mobile racks hold many great advantages. First let's consider the security aspect - If you work in an organization where you don't have your own office and your system has confidential information and you don't want others fiddling with it (say your boss, and all the porn you've been dreading he or she doesn't find out about; for example of course), at the end of the day, when the clock ticks past 5, you can simply pull the drive out of the system and take it home with you safe and secure of other prying eyes.
Or on the efficiency side of things, if you work on more than one PC at work or at home, instead of having to open up your case and remove the hard drive and it's cables, you can simply slide the drive out of its bay and throw it into another PC without having to worry about messing around with cables and what not. If companies like VIP Power continue making our life this easy and hassle-free, we will all become a very lazy race of people. Hell, if you get the right hot-swap software installed, you don't even have to power down your system to remove the drive!
For a practical example, with my former employer I was in the position where I needed to have access to my data on one of my hard drives at work and at home, since the majority of my work was based online. The most obvious solution was to buy a mobile rack for the drive that needed its presence in more than one PC. After spending a couple hours at a local computer swap meet - I decided I'd buy two of these relatively new, and I'll admit what seemed, cheap (they only ended up costing $15 Australian dollars each) looking mobile rack contraptions. I honestly didn't expect much from them - I thought after I opened the box I'd find a product that was cheap in quality and usability and features - I was wrong, very wrong indeed.