OwnCloud is your own cloud and you install it on some station to be the file repository. A workstation, or an Ubuntu server, whatever you have. The stock package in Ubuntu 12.04 is the much older 3.0x. You can use this with the older sync clients, but it doesn't have file versioning and other features of the newer ownCloud versions. You can add the ownCloud software repository from their site. I assume that setting up ownCloud on Windows is a bunch of double-clicking, that seemed like too much effort so I didn't bother.
There isn't much configuration, once it's up your first hit to the web page does the configuration which includes: creating an administrator account, ... That's it. After logging in there are more options like requiring SSL if you want.
Since you likely have a hard drive at least 500GB in size if not multiple TB, this is automatically a much larger repository than you'll get without a monthly bill from cloud services. It's pretty cheap too, a new drive should be under $0.10 / GB these days whereas DropBox is about that per month.
Like any of the cloud services, you can access files via web interface:
There is a "sync client" for PCs and that includes Windows, Mac, and the major GNU/Linux distributions (CentOS/RHEL, Fedora, openSUSE, Ubuntu, Debian). There are also mobile clients but I haven't tried them.
There's ownCloud for you. You can totally replace the big corporate run cloud services if you want or complement them.