For Super Mario Bros. 3‘s 25th anniversary, I present Captain Southbird’s romhack Super Mario Bros. 3Mix. Similar to Rockman 4 Minus Infinity, it implements great ideas from several later Mario games, but this one stays true to the level design lessons of the original. The Rev 1 release from two days ago fixes bugs Mike Matei found in his review, so make sure you get that one.
Update: Captain Southbird has released Rev 2B which fixes a couple bugs, so get that one instead.
Source: https://www.youtube.com/watch?v=ck_a8Y3Gefo via https://www.youtube.com/watch?v=e9rIGa9R9bE via YouTube subscription, also http://sonicepoch.com/sm3mix/