Version: (using KDE 4.4.3) Installed from: Debian testing/unstable Packages Marble should be able to export routes created with "Add measure point". Any file format that Marble can open back is good. The only nice extra feature I can think of is a field of metadata filled in by the user, like "Road to grandma through the wolves' forest".
You can already export a route as GPX file. The difference with the measure feature is that all points should be on a way. But, if a way is missing, you can enter it in OSM ;-)