Types of Flinging
You're going to see a very new type of fling when I get around to making a full map...
Trying to sum up a bit and add my 2 cents:
Easy enough; this is when you place portal A high on a wall and then step out of it. By then placing portal B where you would land, you fly out Portal A with great speed.
The normal fling taught in Portal single-player yes. Can probably be described shorter:
Normal fling
Jumping straight down a horizontal portal and exiting a vertical or slanted portal converting your vertical momentum to lateral momentum.
Just a twist on the momentum fling; portal on ceiling and floor; you build up momentum and eventually place the ceiling portal somewhere else and fling with all that built-up momentum.
I like the name "terminal velocity fling" better, as suggested by someone else in this thread as well.
Terminal velocity fling
Setting up an infinite loop of portals to gain terminal velocity and then replacing the top portal to exit at a new point at maximum speed.
Starts as a momentum fling, but you place a new portal when you land and go through portal A yet another time (or more). Since your entering trajectory is different each time, your angle leaving portal A changes each time, giving you more height/distance, perhaps.
Trajectory fling doesn't have to be that complicated. It doesn't have to be "looped". (Case in point: the original trajectory fling in shmitzchamber01 is most easily done by doing the loop, but can be done in a single pass as well if you get the velocity from the initial entry right. Example: http://www.youtube.com/watch?v=P983h0kevFk.)
In my opinion trajectory in it's basic form should be described as:
Trajectory fling
Purposefully falling through a portal at an angle in order to exit the other portal at an angle.
Done to gain momentum, or height. You are on top of a wall. Place portal A on floor at top of wall near edge; place portal B below on floor at bottom edge of wall. Jump through portal B, come out portal A, and in mid-air maneuver to fall to portal B again. Every time you do this, you leave portal A faster/higher.
Trying to simplify the description:
Step fling
Two portals are placed closed to each other but at different heights. Repeatedly exiting from the upper to fall in to the lower increases momentum.
Jump fling
Jumping through a floor portal on your level to come out of a ceiling portal and then quickly replacing the ceiling portal to the floor to come jumping high out of the original floor portal.
(Meh maybe not much simpler description after all.)
I think that actually covers two different, thought related, flings:
Bounce jump fling
Putting two floor portals on a level below you to fall through one and come jumping out of the other.
Bouncing flings
Repeatedly moving portal sets using the same original momentum.
It's basically a regular fling (or double-fling) but instead of just
shooting for the center, you utilize the "Portal Tunneling" feature
and jump-then-crouch into the EDGE of the portal. The Portal Tunneling
sucks you into the portal faster than you would go through with the normal
jump giving you some extra momentum for a fling with more distance.
I think the term "funnel fling" is more appropriate then to be honest, since it (ab)uses portal funnel to gain momentum. I don't think you need to croush as well, though you get more extra momentum if you do crouch. It's a tricky technique for sure since it requires fairly accurate aim and timing to pull of right in my experience.
Shit flinging: When a map is bad and is bashed on the boards 
Other than that, you guys pretty much made a nice list 
Well, that's the reason I call it crouch-flinging as does a number of other
people ^^ You have to enter the edge so the Portal Funneling feature
pulls you to the center (which requires an increase in momentum done
by the game itself to make you reach the center within the same timeframe
as if you were just aiming for the center in the first place).
As an example, try to do the crouch fling while standing in (non-advanced)
chamber 15 in order to pass the wall (the 2nd fling puzzle in that chamber)
Try that same maneuver when not crouching.
I just loaded Portal and tried doing it without the crouch and I cannot
get enough distance with momentum alone to accomplish that.
If you don't do a "crouching" fling there, you can't get enough distance
to skip the side room that's used for building momentum for those
that DO NOT crouch fling. So, it actually DOES require crouching 
And yes, it is similar to a "normal" fling, but if you crouch after jumping but before
landing in the edge of the portal, you get MORE distance.
Kind of a cross between "trajectory" flinging (considering the way you
have to enter, as I have not gotten shmitz' trajectory fling to work unless
I crouch) and "normal" flinging.
people ^^ You have to enter the edge so the Portal Funneling feature
pulls you to the center (which requires an increase in momentum done
by the game itself to make you reach the center within the same timeframe as if you were just aiming for the center in the first place).
Yeah, I refer to the crouch as well, but personally, I've always had a hard time thinking of it as a fling itself, since its more of a way to improve your speed on any fling you may do. ie you dont do "a crouch fling", but you may choose to do a "crouching jump fling" as opposed to just a "jump fling". Just semantics, I guess.
Step fling
Two portals are placed closed to each other but at different heights. Repeatedly exiting from the upper to fall in to the lower increases momentum.
Sometimes simplifying the description only makes it harder to understand. Thats why I went with the step-by-step description; the above description really doesnt tell you that both portals are on the floor (ie the two portals in a Terminal Velocity fling meet the above criteria as well)
Jumping through a floor portal on your level to come out of a ceiling portal and then quickly replacing the ceiling portal to the floor to come jumping high out of the original floor portal.
Bounce jump fling
Putting two floor portals on a level below you to fall through one and come jumping out of the other.
Some subtle variations on a common theme there. On the Bounce Jump Fling, is it really that important that both portals be below you, or that both be on the floor? Is the true difference between the above two that you used gravity to get your initial momentum in a Bounce Jump Fling, as opposed to a portal use like in a Jump Fling? Or is it the fact that your original portal in a Jump Fling never moved? I just get the feeling that, as defined above, there are 30 subtle variations on these running around. . .
No matter what, this topic is serving its purpose well; there are a few more variations in here to consider in a "flinging" map. Keep 'em coming, if you can!
people ^^ You have to enter the edge so the Portal Funneling feature
pulls you to the center (which requires an increase in momentum done
by the game itself to make you reach the center within the same timeframe
as if you were just aiming for the center in the first place).
As an example, try to do the crouch fling while standing in (non-advanced)
chamber 15 in order to pass the wall (the 2nd fling puzzle in that chamber)
Try that same maneuver when not crouching.
I just loaded Portal and tried doing it without the crouch and I cannot
get enough distance with momentum alone to accomplish that.
If you don't do a "crouching" fling there, you can't get enough distance
to skip the side room that's used for building momentum for those
that DO NOT crouch fling. So, it actually DOES require crouching
And yes, it is similar to a "normal" fling, but if you crouch after jumping but before
landing in the edge of the portal, you get MORE distance.
Kind of a cross between "trajectory" flinging (considering the way you
have to enter, as I have not gotten shmitz' trajectory fling to work unless
I crouch) and "normal" flinging.
This has all originated from crouch jumping for just that little height.
I dont think you guys have heard of long jumping or Circle jumping huh?
In terms of Portal, or elsewhere? 
Why don't you enlighten us?
I suspect your "circle jumping" is what we're calling the "step fling" in this thread, where you put both portals on floors at different heights and go in the lower one and out the upper (rinse, repeat), gaining more height/momentum on each loop.
I suspect your "circle jumping" is what we're calling the "step fling" in this thread, where you put both portals on floors at different heights and go in the lower one and out the upper (rinse, repeat), gaining more height/momentum on each loop.
Nope not at all, its all in the basic Half Life 2 Player code, and was left in Portal, which can be used, heres some videos on it. These videos are from a mod, SourceForts, but this is based of Source, and I had also worked for the mod, so theres no added code.
I've tried all these jumping skills in Portal, and they all work great.
http://www.youtube.com/watch?v=yLyodZnD3A8
The only thing fixed in the player code, was crouch-sprinting, =(.
And yes, running while crouching!
Anyways this was the old way to use your momentum, but now all you youngins, with your Portals! Mainly the skills are Long jump and circle jump, plus hes also using crouch jumping to add into each jump. I would explain how to do them but its very complicated, and takes lots of practice.
Most of this stuff, is like flinging yourself, using only gathered bunny hopping speed and whatnot.
Maybe your portal game is different from mine, but I don't seem to have a sprint button - or a rocket launcher.