I'm currently working on a level editor for Alex Kidd in Miracle World. I've already started a thread over at SMS Power Thread providing some information and screenshots. The editor already contains several tools:
Meta Tileset Editor
Level Layout Editor
Name Table Editor
Box Content Editor
Game Settings Editor
I'm still look for testers so if you're interested you can send me your email address and I'll send you a copy of the current version.
Haven't posted on here for quite a while so the information on here is quite outdated. I've just released a new version with lots of improvements and several new features. For more information on the update see here: emulicious.net/kidded-major-update-released/ For a complete list of features and a download link see here: kidded.emulicious.net/