If you are a Windows user currently you can install VirtualBox which will allow you to install Linux within Windows. Or you could download a Live CD of Linux and play around with it without having to install it. Most distributions have a Live version. Good luck!
Pick up an old P4 box or something cheap but moderately useful, install Ubuntu, and use it daily. This will give you all the "fun" of installing printer, wireless, and proprietary graphics drivers. Use the command line often and be sure to read lots and lots of manpages.