What I use:
HP Laserjet 4+. Incredibly cheap on the used market, Postscript simms
for these are also cheap, take off the shelf ram, toner cartridges are
also incredibly cheap off Ebay, or even from the local Office Depot which
sells refurb ones. The things are workhorses and last forever, they only
need an input roller replacement at 10,000 copies or so, which costs
$100 for a decent printer repair shop, and very few on the used market
ever went this high on the page count. The print server cards that go in
them speak LPR directly to your UNIX boxes. They speak to every Mac
ever made if you like Apples, including the lastest OSX. They have a
panel that is configurable with your fingers you don't need to run some
program that speaks to the printer. Inputs include a parallel and a
port in addition to the network port if you get the network card.
The 4+ will take a duplexer, and an envelop feeder, and a high capacity
paper tray. What more could you possibly want in a laser?
Some colored printer:
Epson Stylus C8x series (C84, C82, etc.) Use gimp-print and ghostscript
to print. Can get full resolution to the printer. Has a parallel port.
The C82 and C84 understand ASCII directly in addition to their epson
that you use to print color with. Cheap. Uses separate ink resivors so
when ONE color runs out you just buy a new one of that, you don't have to
chuck out the entire thing. Ink (once it dries) is impervious to water.
Can obtain ink levels from a program with gimp-print so you don't have to
run Windows for that either.