Many thanks to the ones who are testing this program. greenling, you're too nice...
However, in the next version I'm trying to write an algorithm to automatically build a simplified diagram of the network, similar to the ones you can see at metro entrances and so on. It's quite difficult to write something similar, mainly due to the fact that every savegame has its own structure and dimension, so it's not really easy to define a general model for the graph.
In version 0.2, that you can find here:
http://simutrans-germany.com/files/upload/simuMapViewer0.2.zipyou can find a first implementation of such an algorithm. Til now it's very far from being reliable in every map configuration, however with some parameters/map configuration it succeeds in displaying the map.
Here's a preview of the new functionality:

To access the new functionality, click on the "Railway network" button and adjust the slider on the left, that basically manages amalgamations between the nodes of the graph: greater numbers mean more amalgamation between graph nodes. The "good" value for that parameter is totally relative to map morphology, so I prefer let the user adjust it, rather than impose it from the program. One note: the graph only shows train lines, that are supposed to be longer ones; in the future, I can also extend it for other lines, with really little effort.
When in graph visualization, you can always switch to map view by pressing the same button. As when in general map, you can hide lines by using "Toggle lines" button or zoom the map. In addiction, I added a new button, "Shuffle colors", to randomly change the color of the lines, that sometimes are too similar.
Any testing and feedback is well appreciated!
Cheers