If you have your own Linux web server running Apache, and if you use Mac OS X as your desktop environment, you can serve up your userdir directory with WebDAV so that you can mount it with your Finder as you would an iDisk. The following Apache 2.x configuration enables this. This is not a solution for everyone, it has a number of limitations, but if you just want to use some of your under-utilized network and disk resources this is a simple way to grab a piece of the cloud.