Posted: July 25th, 2006
Last Updated: July 24th, 2006
It seems like this game has been a fan favorite to modify and edit. It's not really a surprise since this game is naturally missing a lot in the gameplay department.
Many hacks can be located at Zophar's Domain on the NES Hacks page (scroll down to the bottom "Zelda 2"). They are in ips format which can be patched to the standard Zelda II rom. One of the most popular and best Zelda II hacks is the "Zelda II - The Adventure of Link 1999" hack. You can download it here. Other interesting hack I found can be located here. This hack features you playing as the infamous character "Error".
The only Zelda II editor out there (for making hacks) can be found on this website. Other resources for Zelda II can be found at Datacrystal, most of the supplied information can be found on the Zelda II ROM map page.
My personal collection of patched/hacked Zelda II roms include somewhere in the ballpark of 10 different hacks. Unfortunately they are all in the rom format and I cannot supply them legally.