An Acronym for Media Transfer Protocol

A newer protocol used by some MP3 players, such as the Samsung U3 series. (Incidentally, the U3 also plays OggVorbis files.) Such players don't use USB mass-storage, so you can't (yet) see them in your file browser window and drag-n-drop files to/from the device like a USB disk.

On linux, support relies on applications using the libmtp library. Applications that support this include RhythmBox (in GNOME) and Amarok (in KDE). Your distribution might also have a package called mtp-tools for accessing these devices from the command line, if you are that way inclined.

In RhythmBox, (at least for the version in Ubuntu 7.10) you will need to go to the Edit menu, Plugins, and enable "Portable Players - MTP". I'm guessing this isn't on by default yet because the support seems a little buggy.