Foreward:
I've been dutifully reading away (It's been hell. Me reading Fanfic is
as painful as chief Wigley being locked in Dunkin' Donuts) and I noticed
that are about thirty or so different usages of the words Chi and Ki
flying around. By no means do I claim to know everything there is to
know about this, or even come close, but I have acquired a bit of
knowledge in my life and figure I should share the wealth. This is
predominately for those who don't really understand it and want some
advice on usage. I may be wrong about any/all of this, but this does
seem to be a pretty constant set of deffinations.

Me finally shutting up and giving my shpiel:
Chi and Ki are different things. Aside from Chi( pronounced Che) being
japanese and Ki (pronounced Ke, both e's are long) being chinese, they
refer to completely different things. 

Chi is Focus. When you concentrate your Chi, you focus on something.
Using your Chi in a punch would mean concentrating completely on the
punch. Also, the better one can focus their Chi, the better they put
their entire body into a punch. 

Ex: I hit someone. I used my pecs, triceps, and a little of my leg
muscles. Ranma hits someone: He uses his pecs, biceps, triceps, waist,
legs, weight, eybrows, and most everything else. Whose going to hit
harder, even if we have the exact same strength? Ranma. (Go figure)

Focusing your Chi on your opponent would usually mean paying extra
attention to his moves and style. It would also mean increased ability
to read emotions and body language. 

Ex: I'm fighting with a four year old for the remote control. He's
winning. I lift the remote up into the air but the little guy holds on.
If I tapped him on the head sharply, he'd probably let go, even if I was
applying constant force on the remote. Reason: he stopped focusing his
Chi on the remote and focused on the top of his head. 

Ki is the energy side of the coin. Ki comes in two types, positive and
negative. Positive Ki is living energy. You have it, trees have it,
grass, birds, aforementioned four year old, they all have it. Negative
is the energy of non life, _NOT_ death. Bricks, rocks, dirt, undead
monsters, and CD's all have negative Ki. There is nothing inherently
evil about negative Ki, but few good guys have any reason to learn to
use it. 

Also, when someone is filled with negative Ki, they don't heal. Since
people can be infected with it through pure Ki attacks, this can be
lethal. It doesn't matter how good a hospital the peron is in. They have
negative a Ki infection, they're probably going to die. That's why bad
guys like it so much.

Yes, Ki is what powers energy attacks. The Mouko Takabisha, Hadoken,
Kamehameha, and others are all positive chi based. I'd bet even the Shi
Shi Hokudan would be positively based, it based on depression not
withstanding. After all, you're not depressed if you're dead. You're not
much of anything.

The ability to tap abient Ki is either called Dragon Chi "Fu Zhensong"
(japanese) if it's positive Ki or Dark Chi "Chakuri-Chi" if it's
negative. Don't quote me on these, I'm only running on one source.
Pretty much everywhere above ground there's ambient positive Ki, pretty
much ebverywhere underground there's ambient negative Ki.

Misc:
In japanese, as far as I've been able to tell, there is no distinction
made between Chi and Ki. They're both called Chi. Hence my usages of Chi
in the above paragraph. 

There are a lot of oriental monsters that can transform completely into
positive or negative Ki. They're invisible, intangable, and weightless
then. They're usually negative Ki and are Infernals, Demons from the
Yama hells. VERY dangerous to someone without knowledge of Ki and Chi.
They usually engage in pure Ki combat. Psionics and magic would probably
not detect them, they all work on different planes. 

Miashara