We write about a variety of platforms here at Lifehacker, and even if you're perfectly happy with what you're using, nothing makes you feel more appreciative (not to mention knowledgeable) than trying something new. Take some of your free time this weekend and give a new OS a shot.
Windows gets a bad rap these days, but it's actually a great operating system. If you haven't tried out Windows 7 yet (or if you haven't used it in a while), check out our master list of Windows 7 shortcuts, and get to know big features like the taskbar and the Windows 7 libraries. Of course, it has a lot of really underhyped features that rock, too, not to mention lots of clever hidden tricks.
Of course, if you've been using Windows 7 for the past few years, you still have some new things to try out in the awesome, upcoming Windows 8. You can download the developer preview now and install it or run it in a virtual machine. It may not be ready to be your primary operating system, but it's cool to see how far it's come in terms of speed and features. Check out our Windows 8 in-depth guides, from the Metro interface (which isn't great without touch, not that it matters) to the desktop, to Windows Explorer and the brand new Task Manager. While you're at it, you can check out some of Windows 8's lesser known features, too.
Mac OS X
If you haven't used Macs since the 80s, now's a good time to take another look. If your desktop or laptop is compatible, you can turn your computer into a hackintosh. They're tough, but with a bit of troubleshooting, you should have no problem getting it up and running. You can also run OS X off a flash drive, or run it in VirtualBox on Windows. The latest version of OS X has some pretty cool features both secret and obvious, especially once you've de-iOSified it (though you can get a lot of those features in Snow Leopard, if you aren't a Lion fan).
Working with Linux is a hefty undertaking, but we've tried to make it easy with our Night School course on getting started with Linux. Of course, if you have used Linux before, you could always try a new distribution, like the super-customisable Arch Linux (my personal favourite) to the netbook-friendly Lubuntu or Archbang. Even if you've done your fair share of distro-hopping, you might try a new desktop environment instead, or even something a bit more out of the box like Chrome OS. Programs like Lili make it easy, by creating versatile, go-anywhere bootable thumb drives so you don't even need to install anything on your system.
Once you've got everything up and running, be sure to check out our Lifehacker Pack for Linux and the Linux App Directory. Check out our guide to getting cool desktop effects in Linux, too, while you're at it.
Putting It All Together: Dual And Triple-Booting
If you like what you see and want to give your new OS a more permanent spot on your hard drive -- without losing your old one -- you can dual boot your computer. We've done guides on how to dual or triple-boot your computer with Windows, Mac OS X and Linux, whether you're on a Mac or a hackintosh-compatible PC. You can also dual-boot Windows 7 and Windows 8, or run all your OSes at once using VirtualBox. Once you've got it all set up, make sure you're able to share your data across all your operating systems, too, for super-seamless switching.