it stays in my closet and dosent make a noice and provides the perfect testing ground for all my wacky ideas =P
Having a personal server is a must for any server side software developer. All you need is a cheap leftover PC, an ISP which does not block incoming connections to the important ports (80, 22 etc.) and a dyndns.com or similar hostname. Try to make it quiet so that it won't disturb you when running in a corner of your home.
If you notice that you need more power, you can upgrade the server later. I had first some years a "PIII 600MHz/384MB/2*160GB/Gentoo Linux" which I then upgraded a couple of years ago to "C2D E6300/2GB ECC/4*400GB in sw-RAID5/1000VA UPS/Debian Linux with Linux-VServer virtualization".