AOL launched the first Mac version of its free online storage service, Xdrive, unveiling a public beta written using the new Adobe AIR platform.

The move pits the online media company against storage giant EMC in the battle to give away storage "in the cloud" to Mac users.

Xdrive Desktop Lite runs on AIR, which takes the functionality of Web-based technologies like Flash and HTML, then combines them with desktop-style APIs (application programming interfaces) such as drag-and-drop, AIR is Adobe's attempt to bridge the online-offline gap.

AOL's beta client was one of the first AIR applications to hit the street Monday. "By deploying this application on Adobe AIR, we have drastically reduced the amount of time it takes to upload a file, and implemented simple drag-and-drop technology," David Liu, an AOL senior vice president, said in a statement.

Xdrive Desktop Lite marks the first time Mac owners have been able to access the service's free 5GB of storage space, which has long been available to Windows users. For $9.95 per month, or $99.50 annually, AOL will set aside 50GB of storage rather than the 5GB free allotment.

Users armed with an AOL email address or AIM screen name can register with Xdrive to open a free 5GB account, said the company. Alternately, consumers can register using any email address through AOL's Bluestring photo sharing site.

The installation downloads for both AIR and Xdrive Desktop Lite can be found on the Xdrive site.

AOL is not the only player in the Mac online storage arena. Apple provides the integrated iDisk and 10GB of online storage as part of its $99.95/year .Mac service., for example, while EMC's MozyHome service gives users 2GB of space for free. Like Xdrive Desktop Lite, EMC's MozyHome is in beta.

Just last month, EMC unveiled a hosted backup and recovery service for Windows based on the Mozy technology, which it acquired in September 2007 for $76 million.