After promising and promising yet failing to deliver their Mac client, online storage firm Omnidrive has finally released this elusive product as a free download. As you can see, the Omnidrive client mounts the remote storage as a Volume in your file system so you access it in the Finder, save to it, open from it, etc. Like Apple's iDisk the Omnidrive client works in the background to manage file transfers, hopefully cutting down on network lag.
In many ways it works like WebDAV, but with the considerable advantage that they have a web client that works properly with Safari and other browsers. This makes it very easy to access your files when your away from your main machine (or to give somebody else guest access to a file).
You can get 1GB of free storage just for signing up, or bounce that up to 10GB, 25GB, or 50GB for respectively $40, $99, or $199 per year. This looks like a good alternative to Apple's iDisk, particularly since 1GB of storage on .mac runs $99 (though of course there are the other .mac services as well). By my calculations, if you maxed out the Omnidrive's storage and bandwidth allotments using instead Amazon's S3 service,with something like JungleDisk, the S3 price alone would run about $14, $66, $165, and $330 respectively. So especially if you're likely to use most of the bandwidth allotment, Omnidrive looks like a good deal.