Newegg recently had a sale on the Fujitsu MX130 S2 micro server for $140 so I decided to pick one up.
Now, I have to say this is a great little machine: AMD AM3+ motherboard, up to 16GB (some users have gone to 32GB) of ECC server dimm memory, 6 sata connectors, 4 drive bays in a small package. You can upgrade to various 95W class AMD cpus. It comes standard with a Sempron single core CPU, 250GB 7200 rpm drive, and 2GB of ram. That in itself is enough to run FreeNAS and you'll have yourself a great little file server. The build quality is very good. In short, this is a micro server class machine targeted to small businesses who needs something economical and green friendly.
I decided to take a little further and upgraded to a FX 6100 6 core bulldozer and added 16GB of ram to make it into a portable testing ESXi box so I can do some virtualization testing. I replaced the stock drive with a 32GB sata boot drive, 128GB SSD, and two 2GB Hitachi 7200 rpm drives.
With multiple cores, a few of drives hooked up, and 16GB of ram, I have myself a little staging lab on my desk. For another $12 and change, I am going to add a secondary gigabit card and an e-sata breakout panel.
I figure I can run 15-20 or so lightweight VM appliances on this thing. Things like a lightweight MYSQL replication, rsync server for backups, GIT/SVN ,etc.
ESXi 5 and XenServer 6 installed with no problems.
For $140 this is a great little box you can use to play around with. It is not going to win any speed tests but for my needs, it is just perfect. I only wish I got a second one.