edit:
Finally I've completed the editors! Well, nothing's really ever finished, but they're good enough to be released.
level-up editor:
download
When you change a value, the displayed number in the level-up dialogue and actual value both get changed automatically.
(If you used a hex editor to change the actual value, the displayed number wouldn't change.)
dialog editor:
download
All the townsfolk dialog pointers in the game are accessible. (not title screen / ending text)
You can change the pointers easily.
Text can be changed with keyboard input or by clicking on a symbol from the game's default tile set.
You can change the text speed.
Includes a previewer so you can see how the text would look in the game.
You have full access to the bank which holds the text, so you can make text longer and relocate dialogs to unused areas.
(There used to be an older dialog editor that I made but it sucked.)
overworld editor:
download update
You can easily edit the maps with a Paint-like interface.
You can change every property of the warp areas, and move them by drag and drop.
You can change the raft locations (in the newest unreleased version).
It tells you all of a cave's connections when you select a cave area.
Quick Test allows you to start the game from anywhere on the map so you can test things very easily.
You can change the palace rock locations.
Includes a user manual that tells you about some of the game's mechanics.
sideview editor:
download

You can change all terrain data.
You can move objects by drag-and-drop. The editor automatically rearranges them.
You can change all enemy data through drag-and-drop.
You can change object types with the radio buttons.
A map lets you see all the room connections stemming from the current one (good for palaces).
You can see a list of every scene that shares a terrain or enemy layout.
Spawn bit checkboxes allow you to control which scenes allow a collectible item to appear in a given section.
You can insert and delete objects into scenes, including collectible items, without messing up anything else.
You can create entirely new terrain layouts from scratch by specifying how many terrain objects you need. New space will be allocated accordingly.
You can change the required palace items without messing up the "turning to stone" events.
Right-click on townsfolk to change their dialog index (Use the dialog editor for actual text editing and reference)
Quick Test lets you immediately jump to the scene you're editing in an emulator to test it out.
Includes a user manual that gives you a lot of insight into how the game puts the sideview together.
Read the user manual or you won't know what you're doing!
The only downside is that the graphics in the editors are rips and don't change.
I've tried to make these editors easy to use by automating a lot of low-level tasks, making friendly guis, including help files, and (my favourite feature) making Quick Test.