As far as an inexpensive NAS I would agree that the buffalo ones are my 
recommendation.  We have a Lacie, which works very well with one access 
at a time, in this case a backup program writing files to it.  However 
when we try to use the Lacie as a place to store images, we are limited 
to only imaging one machine at a time.  If we try to image a second it 
drops the connection to the first.  It would seem the network IO has 
some "limitations".  The buffalo doesn't seem to suffer from that problem.

I would not want to use either in a situation where you had to keep more 
than a half dozen accounts and only the most simple security.  The 
interface for administering accounts and access privileges is "primitive".

Finally, if you are looking for a SAN, shared storage that several 
servers can use, do delve into iScsi.  You can use off the shelf 
hardware to create a very powerful iScsi device.  I've had experience 
with San Melody, software that can take a computer based on a good 
motherboard with a chip set that supports RAID (With WinXP drivers) and 
lots of inexpensive SATA drives and create a shared storage device that 
many servers share.  This opens the door to clustering and having 
virtualized servers automatically fail over should hardware fail.

Another "school budget" solution is to mine CraigsList for fibrechannel 
equipment.  Look for the 1 Gig stuff that is one generation out.  It is 
amazing how fast that stuff is!  Getting it set up will hurt your head, 
but it is good stuff to learn (the switches that connect the storage 
devices to the servers are very complex).  I've never seen storage as 
fast as a Fibrechannel array with 7 drives striped.  It was about 5 
times faster than the fastest SCSI!!!

Craig Lyndes