This is one of the all-time great community game mode projects, a cornucopia of great levels, but the community nature of it means its very uneven. Some levels just aren't as good as the best and the difficulty will jump around a lot.

This is absolutely one of my favorites Super Mario World Hack.
Vldc9 is a annual collaborative hack made by the SMW Central members and the amount of quality put both on the overworld and the levels are great, i highly recommend you giving a try to this game.