A video showing some dunks that get you easy 50s. None require Alley Oops. Controls are listed below.

This is my VERY first video. VERY first attempt at using editing software. VERY first attempt to capture in-game video. So, please be gentle. I hope you all enjoy.

Controls:
T = Triangle (PS2) = Y (XBox)
S = Square (PS2) = X (XBox)
O = Circle (PS2) = B (XBox)
X = X (PS2) = A (XBox)

The 720:
R1+T, rotate left analog ccw quickly, R1+T, hold until first 360 is completed.

The 540:
R1+T, rotate left analog ccw quickly, L1+T, hold until first 360 is completed.

The Double Rider:
R1+O, L1+O, hold until ball touches other hand through the legs.

The Honey Dip:
This one will only get 50 if perfectly executed.
L1+S, L1+T, hold until ball starts moving forward.

The Front Handspring to Double Rider:
L1+O, L1+O, release when opposite hand touches ball through legs.

The Behind the Back:
L1+S, L1+O, Release when ball touches on the other side.

The Rock the Cradle:
R1+S, R1+O, Release when ball is above your head. This one's timing is difficult. Generally, it will feel like you are holding it too long.

The 360 Rider:
This one has many different methods, any combo starting with T or X, and ending with X will generally get you a 180 or 360 Rider. The 360 is a sure 50. The one I did was:
L1+T, Rotate left analog CW, L1+X

I hope you all enjoy! If you have any requests for dunks that you don't know how to do, just drop off a comment!

*Correction: Changed all "Right analog" to "Left Analog". I still had the tosses on my mind. Sorry about that. (less info)