Hey, since it's #Linux
's birthday sort of, how about some links to live CD images from a few distros why not?
Live CDs are neat. You put it into your machine, start up and boot from the CD. You get to run the Linux operating system of your choice without ever touching your existing system. When you get frustrated or bored, you simply restart and BAM you're back in familiar territory. If you really like it and want to make it your primary OS, you can do it right from the CD.
You can also use these to install and run Linux from a Virtual Machine, like Virtual Box on the Mac (https://www.virtualbox.org/
So here are a few, in alphabetical-don't-even-complain-to-me-about-the-order-or-if-your-preferred-distro-isnt-here-I-swear-to-jeebus order: #Debian
: http://www.debian.org/CD/live/ #Fedora
: https://fedoraproject.org/wiki/FedraLiveCD #LinuxMint
: http://www.linuxmint.com/download.php #Ubuntu
A quick note about Linux: I love it, and I find it very easy to use. However, it isn't for everyone, and an unfortunately large number of Linux users aren't the best ambassadors for the OS. Just ignore the holy wars about ... um ... well, everything, and don't engage someone who wants to scream about how you can recompile modules yourself and you're stupid if you don't. Yeah, it's awesome that you can modify your installation however you want ... but the vast majority of users don't want to do that, or care about it. They just want something that works, and I can tell you that -- unlike when I started with Linux in the 90s -- these days it Just Works. And it is awesome.
Existing Linux users: let's be good ambassadors in the comments, okay? Save the arguments about desktops and patent wars for some other time that never happens, why not.