CadEditor

CadEditor is level editor for many classic console games, such as Chip &
Dale, Darkwing Duck, Duck Tales 1-2, Little Mermaid, Tiny Toon
Adventures, Jungle Book, Flintstones, Little Nemo, Megaman 4-6, Contra
Hard Corps, Earth Worm Jim 1-2. It supports about 80 games for NES and
Sega Mega Drive platform.

List of all supported games

There are about 10 games with new levels made in CadEditor, such as:

Darkwing Duck New Levels
Darkwing Duck in Edoropolis
Chip and Dale Alternative
Chip and Dale: Lomax Attacks 

Chip and Dale: Tale Spin levels
Duck Tales - Revision
Tale Spin: Another Shitty Day
Remix of Tiny Toon Adventures

(I don't make hacks myself, and not include any ROM files to bundle, but other romhackers use editor for create games with CadEditor)

CadEditor was designed to inplace edit ROM-files, but it can also be used for epxort maps to Tiled level editor for using map from old games in own projects.

All tools related to project, source code and access are free for users, but you can support project by donation through Patreon