Yes there are three main types of keyboards commonly used today. Actually there are dozens but three that are the most common.
1> Dome Switch keyboards utilize a metal contact that is suspended by a rubber "spring". When pressed down the contact is pressed down on to two contacts on the circuitboard to register the keypress. Most cheap keyboards use this technology. The biggest drawback to this is that the key must be (almost) fully depressed to register the keypress.
2> "Mechanical" keyboards use an actual switch under each key. In the old days these were not the best option as they tended to be clunky, imprecise, and unreliable but technology today has overcome all of those setbacks. Depending on the manufacturer and the design of the switches these can have very stiff keys, very soft keys or any variance in between. The "cherry" keyboards are probably the most famous right now. Many mechanical keyboards use "Cherry" switches and the feel of the keyboard varies greatly depending on which model of Cherry switches are used.
3> The "Buckling Spring" design is a mechanical design that uses a coil spring under each key. As the key is depressed the spring bends and once it presses against the wall in the cavity this causes a hammer (or lever) under the spring to move and register the keypress. The Old IBM Keyboards (and many models made by Unicomp - the people who have the patent) use this setup. Its advantage is that it provides an audible and mechanical "click" to let you know the keypress has been registered long before the key reaches the bottom of it's travel. This translates into faster typing and less wear and tear on the keyboard itself.
Many people debate over whether #2 or #3 is better and to be honest today both options provide a very similar experience, but nearly everyone (who touch types) can agree that both #2 and #3 are vastly superior to #1. The only advantage #1 has is price... and flexibility. You obviously can't have roll-up silicon keyboards that use #2 or #3, and many laptops simply don't have the space for anything but the #1 method.
Now I find it kind of amusing that people are bringing up $100+ mechanical keyboards when Jayhawk's main point is that the $80 for a Unicomp keyboard is way too expensive. The Optimus Maximum keyboard I posted a pic and link to was just me pointing out that the term "expensive" is a relative one. Personally I feel that $80 for a keyboard that works great and last for years is an excellent bargain. Others may argue that that are willing to spend $150+ (or even thousands) and still consider it to be a bargain. And then there are those who are perfectly happy with a $10 keyboard and see no reason to spend any more.
And I can't argue with that logic. Until my last three keyboards I was using second hand keyboards from my stash in the basement. Old HP, eMachines, or Dell computers that I had saved from computers that I had worked on that were worth fixing. When all of them finally failed (got only knows what abuse they endured before I got my hands on them) I found a fantastic sale at Target for a basic wireless keyboard and mouse (for $14). Those worked great for almost a year but I got tired of messing around with the whole battery deal. Seemed like I was having to change and recharge batteries every couple of weeks on my mouse and my keyboard would last a couple of months but then randomly miss keystrokes and the like. New batteries seemed to help but I got tired of messing with it.
Then I bought a "decent" wired Logitech setup.. a keyboard and mouse for $50. I used the mouse for only a couple of months but I never could get used to it. It was a "palm" type of mouse where you put your whole hand over it and I was used to "fingertip" mice where only my fingertips would touch it. I got a refurbished RAZOR Salmosa mouse from Woot.com for $13.37 and I love it! Been using it for well over a year now! The Logitech Keyboard on the other hand gave up on me after only about six months. The paint had rubbed off of many keys already. Many other keys would intermittently not register keystrokes. Whatever. I bought a cheap Microsoft keyboard for under $10 at a local "Office" store and it's been going well for several months but I catch myself making typos frequently. I don't know if it's me or the keyboard.
I do know that I used to type 100wpm years ago on the old IBM keyboards in high school and today, even with many years of typing experience under my belt, I still struggle to hit 80wpm... honestly it's usually closer to 60-70. A big part of me has to wonder how much that has to do with the keyboard itself. I would have no issues spending $80 on a quality keyboard if it was more comfortable, allowed me to type faster, and lasted for a long time. Heck I've already spent almost that much as it is on replacing inferior products!
