Well, in that post on telescopes I put up the other day, there were plenty of manufacturers, web sites, and commercial sources that I could recommend. Microscopes, though, are another matter. There's no equivalent to the amateur telescope making/modifying community. One reason for that is that we're talking about lenses for magnification, rather than big mirrors for light-gathering, and mirrors are a lot easier to make (and test) than lenses, particularly combinations of lenses. Microscopes can also have more mechanical parts than telescopes do, and these parts are less modular, which can make the used equipment market rather tricky. The new equipment market tends to divide into "Wonderful, really expensive equipment for research" and "Cheap crap". (More thoughts on the similarities and differences between the amateur astronomers and microscopists here and here).
But not always. Here's a good site with a lot of buying advice, and here are more good sets of recommendations. You'll have heard of the brands of the most common laboratory microscopes (Nikon, Olympus, Leica, Zeiss), and there are a number of lesser-known brands, which I would assume all use Chinese optics (Omano, Motic, Accuscope, Labomed). The advice, as with telescopes is to Avoid Department Store Models, but beyond that, I'm not sure where to send people. Reputable dealers seem to include Lab Essentials and Microscope Depot, but be sure to read up on those recommendations before purchasing. An older microscope in good shape probably has the best price/performance of all, but that's not a casual purchase, for the most part. For what it's worth, I use an old "grey metal" Bausch and Lomb, purchased back in the 1970s used from around the University of Tennessee medical school.
Update: as those recommendation links say, there are two big choices: a stereo microscope or a compound one. The former is good for looking at whatever (larger) object you can put under it, while the latter is higher-magnification and needs, in most cases, to have something that light can pass through. I'm partial to protozoa and algae myself, so I have the latter, but the former is a very useful instrument, too. A great general reference for someone getting into microscopy is Exploring With the Microscope.
If you're into pond life as well, two excellent references are How to Know the Protozoa and How to Know the Freshwater Algae. I own both, but then, I'm a lunatic, so keep that in mind.