You basically want an SLR camera - so you can see exactly what you're taking
a photo of, and it helps when messing around with different lenses, filters
or anything you care to put in front of it.  I also recommend a 35mm (i.e.
film camera) - it's much cheaper than the comparable digital SLR, and should
you wish to sell it again, it'll probably pick up much the same price.  You
also want a fully manual camera to learn on - it forces you think about
aperture and shutter speed.  Your photos will only be as good as the lens,
so, to start off with, avoid any zooms that aren't professional - go for a
50mm f1.4 or 50mm f1.8 or f1.7 etc. as these result in similar perspective
to the human eye.  Second hand Pentax, Nikon or Olympus would be a good
starting point - due to excellent optics available for reasonable prices.
Have a look for these models:

Pentax MX w/ Pentax SMC-M 50mm f1.7 (or even better, f1.4) - these retail
for about £120 with a lens, but can be got for cheaper.  They are fully
manual, and very well made.

Pentax ME Super w/ above lens.  These retail for £60-70 with the lens.  They
have semi-automatic metering, as well as fully manual.

Nikon F2 w/ 50mm f2 lens.  More expensive and very heavy, but can be found
in around the £200 region.  Special feature is the removable 100%
viewfinder.

Olympus OM-2 w/ 50mm f1.8 lens.  Costs around Pentax MX prices, and an
excellent camera, too.

Apart from the Nikon, all of the above are very light and portable cameras.
The Nikon weighs a lot, but is incredibly well-made.  The MX doesn't
compromise on build quality while still being very compact.

Duncan.