MP3.com, together with Michael Robertson (Lindows/Linspire founder) has through the MP3tunes.com site launched the Oboe service, which allows users to upload their digital music collections to a secure "locker" and then access it for playback from any web-connected computer.
Oboe supports not only MP3 files, but WMA, OGG and AAC formats, and runs on Mac OS X, Windows and Linux systems. DRM-protected WMA and AAC files, from licensed digital music services, are not supported, at least not for playback, though they can be archived.
MP3tunes.com is offering both free and premium accounts - the latter cost $40 a year and enable music lockers of unlimited size, "no bandwidth charges", the ability to automatically sync your music collection and the locker, and listen to 128Kbps streams. The free version limits streaming to 56Kbps, allows uploading only through the Oboe Firefox plug-in and doesn't do syncing.