If you just want something to post on the net buy any cheap scanner
that will take medium format, a lower cost flat bed scanner. If you
want to scan and print, upgrade. Nikon film scanner will be outstanding
but expensive. Get a flat bed as a compromise.

If you have good prints of above proof size, you can do a decent job
for web display with nearly any flatbed scanner.

If you want to scan the slides/negatives and work from there
(essentially doing the "printing" process of color and density control
in Photoshop), then you need a considerably better scanner.

Start from what size you want to put the photos on the web at -- let's
say you want a photo to fit within a 600x600 pixel square on the
screen (many people choose a smaller size than that).  Now consider
what size your negatives are, and calculate the number of pixels per
inch on the negative you need to scan at.  

Actually, I'd scan at 1.5x or 2x that resolution, based on my
experience of working from film.

To get that, you need to scan at (600*2) / 2.25 pixels per inch, or
533 pixels per inch.  So, as you can see, you don't need an especially
high-resolution scanner to do this job.

What you *do* need is a scanner that produces *good* pixels, and a
scanner that's capable of handling the max density of what you've got
-- slides having a much higher dmax than negs, of course, and being
correspondingly harder to scan.

The "best" choice is a medium format dedicated film scanner, which
will be *far* better than you need for this and very expensive, but
will give you the best results you can get yourself.  (Well, you
*could* buy a first-rate drum scanner and learn how to use it, but
let's be reasonable.)  The Nikon Super Coolscan 9000 ED should be
marvelous.  It does cost nearly $2000, though.

The much more affordable choice is a flatbed scanner with transparency
adapter (well, they tend to be built-in these days).  These will have
perfectly adequate resolution; what you'll need to look for is one
that has good enough dmax.  Epson makes some reasonable choices last I
checked.  I'm using an old Microtek that works pretty well even for
moderate sized prints.

Look at the Konica Minolta Dimage Scan Dual IV. It will do what you want
and it only costs $230 at B&H. Very good value, but you will have to
clean up the dust and scratches yourself as it doesn't have digital ICE.

   Well, you could buy a film scanner. I have the Minolta 5400. It is an
excellent scanner with good dynamic range but it is expensive and the
software has lots of quirks. It takes about 20 minutes to scan one slide at
high quality and it needs a lot of memory with a fast computer.
   If you are planning on scanning just a few pics I would think about just
having a store do it for you. You should try a few stores to find out how
much it would cost. Typical cost is $1-5 per slide, maybe not the best
quality but adequate. If you plan to scan fewer than a hundred slides it
might be better to do a one-at-a-time job. You'll have more cash for other
things, and when you switch to digital you won't have a dinosaur on your
desktop.

Dave