Zelda Indigo is a mod for Ocarina of Time that is currently in development and has a pretty substantial demo available for it.

I've been watching ZFG play through it in some highlight videos and it seems pretty awesome. It's basically a sequel to Majora's Mask following the Hero of Time. It would be cool to one day play through Ocarina of Time, The Missing Link (another mod), Majora's Mask, and then Indigo to get the full "Hero of Time" experience.

The only downside I can see with the mod at the moment is that it's not exactly lore-accurate. It's sort of lore-friendly, but the creator's writing makes a lot of jokes relating to the Ocarina of Time modding community that kind of kills the vibe a little bit.