The level file format has been specified
I looked around for some tagged binary format that fit my needs, but everything was either waaay too complex or failed to do what I wanted, so I ended up rolling my own.
You can read the full level file format specification here.
As soon as I get it working well, the indev version of the game will be able to load levels in that format. Possibly tonight, probably tomorrow.
I encourage you to write level editors, loaders, generators and whatever else you can think of! =D