Google's Drive file storage and syncing service is now available, with 5GB of free storage.

Small businesses and enterprise can upgrade to 25GB for $2.49/month or 1TB for $49.99/month. Gmail account storage is increased to 25GB with a paid Drive account. 

The service is built directly into Google Docs and it is integrated with other Google's products like Google+. 

Drive, which provides you with access to cloud-connected storage on PC and Mac desktops and Android phones, competes with Dropbox and Microsoft's SkyDrive.

I'm using it and it seems pretty useful. It works better with Chrome browser, especially if you want to upload folders, not just single files.

A final note: although the service is live, it's not available for everyone yet. You can request that Google notifies you when is ready.