That's always the first question I get when it comes to learning Microsoft Technologies on your own. I'll say first, if you have a computer that is 3 year old or older a lot of this won't apply to you, sorry, newer technology is needed for this.

I have three computers right now

Microsoft Surfacebook Pro

Lenovo Thinkpad T1000

HP DL380 G5

The important thing to know about your hardware, even if it is older than 3 years is it capable of doing virtualization and x64 bit software. Best way to guarantee that is anything Intel Core 2 Duo and above or AMD Athlon 64 and above.

So back to where I was. Any of these products can be installed in a Hypervisor, software capable of letting you create a virtual computer, like Microsoft Virtual PC, Microsoft Hyper-V (available on server OS and Windows 8), VMware Workstation, Fusion (for Mac), Citrix Xen Desktop, Oracle Virtualbox (Free) just to name a few. I user VMware workstation when I'm on my desktop PC for quick one-offs but I also dual-boot all my machines to Windows Server 2008 R2 Enterprise Edition for Microsoft Hyper-V. I also use Oracle Virtualbox well because it's free and VMware Workstation is expensive for the novice but has the most features (in my opinion)

So for all your DIY'er out there, get a PC (Or Mac but I won't cover that much) with 4 core CPU, 8gb RAM (at a minimum) and a couple terabytes of hard drive space (VM's can take a lot of space but we will cover that as well) and again, make sure your computer can either do Intel Virtualization (VT-x) or AMD Virtualization (AMD-V) and your all set.

If building one is not in your skillsets, you can buy a used Dell/HP/IBM or white box on eBay or Craigslist. I go down to the city Recycle Center and find Servers that can be pieced together to make another working machine, free for you. Just takes a little patience from your significant others

Again, most of what I will show here is either Hyper-V or VMware workstation.

******UPDATE*****

With windows server 2012 and newer a new version of Windows Server has been created for FREE. Microsoft Hyper-V Server 201x is available. Free to use (for your business) but they get you with the management costs, SCCM, SCOM etc. It wil be covered on this blog as well.