Apple has recently created a new server based on their tine footprint Mac Mini cases. These machines are great little servers for small offices or even at home. Just compare how it stacks up next to other servers in its class:
Mac OS X Server is a wonderful server platform with very easy to use set up and configuration tools. Even though the machine is running Mac OS X, it could easily provide files services for Windows, and Linux as well as Macs. Actually, the ability to provide things like Windows File Sharing, LDAP, Web, FTP etc. can usually be enable with a simple checkbox.