Written in C#, the Pocket RPG Maker project is now in its final stages and should be released sometime during the next few weeks. With support for VGA, this editor will allow you to create an unlimited-sized two layer map using RM2K tilesets. You'll be able to switch to an area-editing mode to set active/inactive areas of the map, and to top it off, you will be able to save, load and test maps on-demand. For more information, visit the developer's website
here. We'll keep you posted with an update as soon as it is released.
Edit: Updated with a newer screenshot.