The most awesome Mario versions in Flash
From article on Sharenator.org
Tuper Tario Tros (Super Mario + Tetris)

This is what happens when you combine two of the most successful classical games ever. Very original and really difficult game.

Play Super Mario Bros as Bullet Bill. You control a Bullet Bill with the arrow keys through each of the 8 levels, hitting either Mario, Luigi or the flag at the end. If you like this game, check out Bullet Bill 2.

Probably the most awesome Flash Super Mario ever created.
"Super Mario 63 is a fan-game inspired by Nintendo's Super Mario 64. Many levels and features are based upon it and other of Nintendo's games, but a variety of them are completely original."
Warning: This game may take some time to load (it's a 14 MB file)