The keyboard and mouse are your primary mode of input.  Why spend 5 dollars on something you'll be using daily for hours?  It makes sense to buy a quality product that will promote your long term health.  (Repetitive motion damage is nasty.)  I've spent a bit of time looking around at the ergonomic keyboard and mouse offerings and here's a little run down of what I've found:

Keyboards:

Flat keyboard:
Crumby ergonomics.  You usually have to reach a little to get to all the keys.  Often used keys (backspace and enter) are in poor places forcing repetitive motion from your week 'pinky'.  These often put your hands at a higher elevation than your wrists cause subtle wrist strain.

Microsoft Natural Keyboard:
A step in the right direction.  These keyboards put your hand and wrists in alignment a little better (assuming your posture is correct.)  The keys are a smidge closer, but still require some reach for corner keys and function keys.  (And enter and backspace are still in the pinky zone.)

The Kinesis Maxim and Evolution:
Now we're starting to get into the goods...  These are like a Microsoft Natural keyboard on steroids.  (And the price is on steroids to.  But your wrists are worth it.)  These use many of the same ideals as the Natural keyboard, but to a larger degree and with finer precision.  I have never actually used one, but I've read many reviews and papers on them.  (I like Kinesis.  They make good stuff.)

The Maximum (left) and Evolution (right) keyboards.

The Kinesis Contoured Keyboard:
My keyboard of choice!  I use it for everything.  (Mine is the Classic model.)  This keyboard is much different than most others out there.  (Check out the picture.)  The keys are in 'bowls' and are in strait lines rather than diagonal.  Enter, backspace, alt, ctrl, pageup, pagedown, home, and end are all under your thumb.  Every key in the dish is within easy reach with no wrist motion at all.  (You may have to move a tiny bit to hit the function keys, depending on your wrist size.)  Moreover, you can remap keys, program macro's, and there are two keysets.  (Hit a button and the right bowl becomes a 10 key.  The left becomes...  well...  remap it to whatever you want it to be.  It's great for games!)

The Kinesis Contoured Keyboard.  This baby rocks!

Chord Keyboards:
These are keyboards with very few keys.  You press different combinations at once to make different characters.  That means learning to type again.  And since you usually hit the same button with each finger over and over, it seems that it might actually be a bad thing.  They come in a lot of different shapes.  I can see how it'd be cool to have one (and know how to use it.)  But for myself (and most users I know) it's more trouble that I'm willing to deal with.

DVorak:
DVorak is a way of laying out keys.  The two most common key layouts are QWERTY (what you're probably using right now) and DVorak.  (What I'm going to learn to use when I have a lot of time to kil.)  DVorak puts all the most commonly used keys on the home row and balances them between sides.  (Ever notice you use your left hand more than your right when typing?  That's because QWERTY sucks, to be blunt.)  DVorak also works to make your fingers drum inwards.  (If you've ever used it, you may have noticed that your fingers don't leave the home row very often and they seem to flow towards the center of the keyboard with each word.)  DVorak it cool, but requires learning to type all over again.  (I tried it once and got up to 25 WPM then gave up.)  The upshot is, with windows, a few minutes in the control panel can have you set up to use either layout on your existing keyboard.  (And change layouts on the fly.  I'll write up some instructions for setting this up a little later.)

The Dvorak Keyboard Layout.

Mice:

Average everyday mice:
A bit to small to hold your entire hand.  And typical mice tweak your wrists back a little.  (Enough to hurt you.)  Gel pads on your mouse pads help support your wrist.  I highly recommend these.  A typical mouse is really bad for you.

The Microsoft Optical (explorer) Mouse:
I think this mouse is very cool.  If feels good, supports your entire hand, tracks well, and all the buttons are just right there.  I would buy this mouse, but I found one I like just a little tiny bit better.

The Razor BoomSlang Mouse:
This is a very odd looking mouse.  It's flatter, wider, and provides more support.  However, it's conceived as a high end gaming mouse.  I feel it fits the job because it is highly sensitive.  It takes getting used to, but when you have the sensitivity cranked up, you can get everything done without moving your mouse more than an inch or two.  (Less motion = less motion strain.)  It's not optical, but it performs like a champ tracking better than any other ball mouse I've tried.  Here's a link for ya'.

To be real honest, those are the only mice I've looked into.  There's others, but I haven't checked them out yet.  When I do, I'll add them.  Until then, keep on truckin'.