No flash plug
I know there's a level smoothing algorithm in iTunes, but as McDSP say, it doesnt work all that well. So they've crearted an app which takes advantage of their nowse in the field of limiting and compression and come up with their own app Louder Logic. Its designed to give a more even volume between tracks and also within the same track, if the dynamics are wide and your listening environment is challenging.
There's a free version and a paid one $3.99
This crazy oscillator now has even more features