I saw the article called SuperMarioWorldTricks, and I thought it was really useful, but it leaves out a few things.
Here's the original article:
http://www.tasvideos.org/SuperMarioWorldTricks.html
Speed falling while flying backwards
When your flying and your using the speed glitch to maintain 51 subpixels, you cannot press forward or you will loose speed. This is bad because you may have to fall quickly or you might hit a wall, miss a block, ect. So use the turn around while flying glitch, and when your turned around, press ← and → at the same time and you will fall quickly, but loose no speed.
To use that fall to gain hight, turn around while falling again, and then press ← (or → depending on which direction your moving) for 11 frames, and you'll keep your speed of 51.
Fly While Moving backwards
When you are moving backwards and flying, you can actually still catch air. If you are catching air normally, and not using the glitch, press the opposite run button (either X or Y). Now if Mario is facing an angle lower that 180 degrees, simply press the direction you wish to move for 9 frames, then press the opposite run button (Either X or Y) and you'll catch air.
If you want to use the air catching glitch, press the direction you moving for 1 frame, let go for 3, press it for another 1 frame, and then press the opposite run button (again, either X or Y)
Mid-air shell jump
First off, you cannot be using the hopping glitch while doing this. You also cannot be moving upwards, or downwards too fast.
When you gain sprinting speed, jump into the air for however many frames. When you are at a good angle, press ← for one frame, → for 7 frames, then throw the shell. If done right you will land on the shell while its moving in midair
Key jumping (improved)
In the original article, it says that key jumping can only be done near a wall. Untrue. It's actually very easy to do without a wall.
While you are still moving upwards, but slowing down, let go of the key. Now move yourself towards the key and just land on it, jump off of it and grab the key, and repeat. This is a very common technique, and I'm surprised that it wasn't listed before.
Staying on ceilings with yoshi
If you find a ceiling while on yoshi, you can stay on that ceiling as long as you want. 2-4 frames before hitting the ceiling, press A for one frame, let go for one frame, and repeat. You can move around while doing this, but very slowly
Jumping through sprite platforms with springboard
First off, sprite platforms include turn block moving bridges, grey falling platforms, timed lifts, ect. Immobile sprite blocks include light switches, message blocks, and the unused sprites, invisible used block.
To go through these platforms, just throw the springboard up in the air so that it will land on the sprite, and make it land on you. This will make Mario jump off of the springboard, but fall right through the platforms.
You'll know it is a sprite block if it is either moving, or you can throw items through it.
Spring board Y axis speed abuse
I'm not talking about portable springboards, I'm talking about the green platforms you find in the first level of the special world. If you jump a few frames below a green spring board, it will pull you upwards. This can save very few frames.
Invincible Goomba
If you normally throw a goomba at an enemy, it kills itself. If you throw it 3-4 frames before hitting the enemy, it will kill the enemy, but stay alive. This does not work on enemies that die in a poof of smoke