How technically "fluent" are you?
Because for geeks like me, an interesting solution (and nice week-end project) would be to build yourself a Linux NAS. You find a old PC, add a 40$ PCI ATA133 controller if the PC doesn't have 4 PATA ports (8 drives ... you will need 1 for CD/DVD), create 1 big LVM (kind of software RAID) or use the controller's built-in RAID combined with LVM to create one big disk. Share that disk through SAMBA, NFS or anything else you would want.
Dedicated off-the-shelf solutions exist, but they are mostly professional and can easily cost 500$ and up.
You could also try to find yourself a home NAS (not cheap either) or look for a NetDisk by Ximeta (branded as
ComCast in Canadian FutureShops). What I like about this product is that once you install drivers and configure the device, the network drive works just like any other drive (but slower due to RJ-45 interface).