PersonalTech Pipeline has an interesting article on how to build your own terabyte file server for far, far less than you could ever buy one:

For our 1 Tbyte NAS/file server, I chose a different tack, using a standard PC as the host hardware. Shared storage via a PC can deliver the same effective benefits as a vanilla NAS unit while also offering a few advantages. For example, it uses standard, commodity-level parts and familiar, well-proven technologies. Not only does this keep the prices down, but it also means all your normal PC knowledge applies--there's nothing new or different to learn. And because the server is a normal PC, it can also be used as such, performing any and all normal PC tasks in addition to the NAS-specific task of adding massive storage to the network. Having the storage in a standard PC further means you can have direct access to the 1 Tbyte of disk space (as opposed to network-only access for a classic NAS unit), and your 1 Tbyte file server can act as a backup or spare PC for your operations. Familiarity, low costs, high operational flexibility--there's a lot to be said for this approach to massive storage!

The heart of the system is this Intel motherboard, shown in Photo One with the 3.06 GHz CPU installed, the heatsink and cooling fan mounted, and the 512 Mbyte RAM bank in place. The motherboard has many features built in, including Intel Extreme Graphics 2, onboard 10/100 LAN connection, PATA and SATA support, six-channel audio, and the usual array of USB, PS/2, and other ports. The rest of the bundle also looked good. The 450 W power supply was ample for our array of drives, and the capacious, well-ventilated case provided plenty of room to work in and to mount our drives.

Four 250 Gbyte drives provided the 1 Tbyte (1,000 Gbytes) of storage for our system. Like everything else in this discussion, the specifics are intended just as an example. But in this case, I located 3btech.net via Froogle.com. They offered the drives for $81 each, including a six-month warranty. This was the normal price, not a rebate or special or a "one drive per customer" deal. Four drives, totaling 1 Tbyte of storage, cost me $324, bringing our running total so far to $514.