Sansa Fuze(+) doesn't work out of the box with the current version of rythmbox or banshee with Ubuntu 10.10. Here's a short description how to get it work.
First of all you need to create a file with the name .is_audio_player in the root directory of the multimedia player:
#e.g. command for the Sansa Fuze+ touch /media/SANSA\ FUZEP/.is_audio_player
After that you need to configure the file:
#configuration for Sansa Fuze+ audio_folders=Music/ folder_depth=2 output_formats=audio/ogg,audio/mp3 cover_art_file_type=jpeg cover_art_file_name=folder.jpg cover_art_size=300
After that the Sansa Fuze(+) should be displayed on rhythmbox or banshee and you can simply drag & drop your music to the player.
The original explanation is from the following website