While working on our game, we’ve decided to load maps i.o. randomly generating one. We are using Tiles for the ground and GameObjects for things that stay on the ground(Tile). What is the best map editor I should use for now? We also prefer GZip files. Thanks for any help! 
I don’t know which is the best map editor. But Tiled seems to be apopular one:
We already tried this one but we are not sure which map file we should use.
see if a map format they offer seems sane for you, if not specify some format yourself.
Just use the tool, because it will save you so much time in comparison if you decide to build some yourself.
I find Tiled very good for tiles.
It is also OK for rectangular, free objects but not so good for polygons and lines.
Woah. Wasn’t tiled open source once? I faintly remember that you could look at the java source or am I getting confused with something else?
So far I know Tiled is written in C++.
It was ported from Java but there are still some features in the Java version that haven’t been ported yet. You can still download the Java version though.
The source for the Qt-version is available