Could anyone please refer me to a good website about piano proficiency grades (for lack of a better expression) and/or the exams/evaluations related? Thanks!

If you're in the UK, the Royal Music Board change the piece you need to play in the practical every year, if its non piece, thats always to some form of constructed basis.

If Your in Canada, The Royal Conservatory Of Music.

Thanks guys, but unfortunately I am in the US.

hey, well i know there is the AMEB in australia
but also in london i think is the Trinity
which does grading throughout all the world.
so if you want to look at grading i would recommend
the trinity.

Free sheet music @ http://www.mx-music.com