Tom has an (again) excellent article about a very affordable NAS-solution. It plugs right into you controller and in about 5 minutes you have yourself a NAS.
The system is based on Open-E’s license-free NAS operating system, and comes in an Enterprise (NAS Enterprise), a normal (NAS 2.0) and in a small (in features) version (NAS SOHO). With prices ranging from approx. 200 euro to about 600 euro, the solution is much more cost-effective than a real NAS, since you would have to buy an extra disc for the operating system, the operating system itself and perhaps some client licenses as well! The concept of Open-E’s NAS is to buy the hardware, and you’re done buying.