I'd like to know more about the editor. Did you roll your own? What does the file format look like?

I made the editor myself. It is using GTK and OpenGL. It is a rather simple GUI ([url="http://www.gamedev.net/gallery/album/86-editor/"]"Editor" gallery[/url]) above the main data classes of the game (objects, players, emitters, materials, ...).
Everything is stored directly in the game format: various text files easy to read/edit by hand when needed (it was useful at the beginning, before the editor existed).
I have the following files:
- "emitters": defining the particles emitter types.
- "level_xxx.tiles": x and y size followed by the the indices of each tile.
- "levels": the main file defining the content of each level; level properties (fog, ambient, wind power/direction, ...), objects (type, position, associated mesh, speed, energy, ...), players (controlled object, AI level, weapons, ...), emitters instances (type, position, state, ...), lights, cameras, events and sounds.
- "materials"
- "tiles": definition of each tile usable in the levels
- "weapons"
Except for the "level_xxx.tiles", every file is made a bit like INI files:
[SECTION1]
PROPERTY1: value
PROPERTY2: value1, value2, value3
...
It is rather low-tech but is good enough for my needs. XML would have been a good choice if everything was in the same file I think. A binary format could have been a lot more compact but not flexible enough for the beginning of the project. It is still possible and not very difficult to write something that converts my text files into a binary format but I don't need to.