Amazon has officially announced their Cloud Drive this week. Amazon Cloud Drive is Amazon's version of online file storage. It comes with 5GB of free storage and you can upgrade to 20GB of storage by purchasing an Amazon MP3 album. There are also other levels of storage that you can pay for (up to 1000GB for $1000/yr).
The service does not mention anything about file syncing, just that you upload your files to their servers and then you can access the files from any computer. You can upload documents, musics, photos and video and download and preview them from any computer.
You can stream your music files from the service and any music you purchase from Amazon are stored on the Cloud Drive for free and don't affect your storage capacity.
It's another option for cloud file storage. I don't think it is as useful as Dropbox, Sugarsync, Zumodrive, Box.net and others because it does not sync your files. You have to manually upload them and then if you download and make changes, you'll have to re upload them. You can only download 1 file at a time.
There is no support for Apple devices yet. There is an app for Android though.
Another issue is that many schools block Amazon as a "shopping" site so you won't be able to access your files. However, if you purchase music from Amazon, this is a great idea because you can stream your music from anywhere.