It would be great to have an optional Rockbox feature that could either automatically move or delete files after they have been listened to. This feature could be useful to people that listen to a lot of podcasts and multi-file audiobooks.
For example:
A user could have a "podcast" and a "music" folder on their player. The user would be able to turn on this feature for the "podcast" folder that would automatically move each file into a "listened" sub-directory after reaching the end of the file. Or if they didn't care about loosing the file, they could have it deleted automatically instead. The files in the "music" folder would not be affected by this option.