Amazon.com on Tuesday unveiled “Cloud Drive,” a new service that enables users to keep music available online. The service works in conjunction with a “Cloud Player” app that runs on Android devices; an app build using Adobe AIR is also available for the Mac.

[ad#Google Adsense 300x250 in story]Cloud Drive enables you to upload music you already own and music you purchase through Amazon.com’s MP3 store to Web-based storage, where you can access it from your Android device or computer.

Because Cloud Player an Adobe AIR app, it won’t work on the iPhone, iPod touch or iPad. AIR is built using Flash, which isn’t supported on iOS devices.

Users of the Cloud Drive service get 5GB of storage capacity for free; customers who purchase an MP3 album via Amazon.com can be upgraded to 20GB of free storage for one year; additional storage plans are available. New purchases are saved directly to Cloud Drive and don’t count against your storage quota, according to Amazon.

Files can be stored in unencrypted AAC or MP3 formats and retain their original bit rate. You have control over what content is uploaded to Cloud Drive – songs, albums, playlists.

Cloud Player for Android is bundled with a new version of the Amazon MP3 App now available for download. Cloud Player for Web works with Macs equipped with Firefox, Safari or Chrome.

It has been widely speculated that Apple is working on its own cloud-based service for iTunes, but Apple has not yet tipped its hand.