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Claire asks about displaying electronic maps in the classroom.  I think
you should really consider the more generic question of classroom
projection systems for computers.  The reason is that the same issues
apply to projecting nearly everything but straight text (and if your
faculty are doing only that, you might want to rethink altogether ;-)
 
Anyway, I have been doing projection of computer screens for something
like 8 years now and have used practically every kind of alternative
projection system from GE PJ light valves ($100Kbucks and up) to
the new CCD projectors to Barcos to color and wimpy monochrome LCD pads.
 
There are basically three issues:
 
1.  The amount of detail and number of colors you need to project
2.  Whether there is movement on your computer display, i.e., animation
3.  The size of room you need to project into, i.e., the size of
    the audience
 
With respect to item 1, if the detail is basically a single pixel wide
in your computer graphic, you won't be able to see it except with a
Barco.  If you have more than 8-bits of color (256 colors) you need
a Barco or better.
 
If you will be showing multimedia or video through window, you need
a Barco or better.  If you have movement on your computer screen as
with animation, it gets very smeary on nearly every LCD pad I've used
(one exception; I can't remember the brand now, but it was in
Europe).  In one of my presentations, I have video which plays back
on an NTSC screen or on a 24-bit color computer screen just fine but
looks really crummy on anything but a Barco or a CCD projector.
 
If you will be projecting into a room of less than about 100 people
and are not otherwise constrained as above, a color LCD panel will
probably do for you.  If it's more than 100 and less than about 275,
look for a Barco or equivalent projection system.  If it's more than
about 275 or 300 people, try to get a CCD projector (these have
basically replaced the GD PJ light valves and give absolutely
excellent quality projection in rooms up to at least 4000 people
-- that's the biggest crowd we've ever had).  The one remaining issue
is that you'll have to have a REAAALLLLY big screen if you have to
go to the CCD projector (like 16' by 20' or bigger).
 
HTH.
 
virginia(I have a bazillion parts but none of them are spare)h