I've had a free 1GB box.net account for a while, but haven't used it in any anger beyond uploading a bunch of my how-to documents as a test.
Today I tried adding a WebDAV connection to my GNOME installation - a trivial act of specifying the correct URL, https://www.box.net/dav and then entering my box.net credentials in Nautilus. This worked pretty well so I repeated it on the Mac. This was also successful.
So I now have easy access - WebDAV but also the web interface - to a bunch of storage online from all my platforms. Should be good for storing those (non-private) things that I might want when I'm out and about.