Oracle Webcenter looks like total overkill and, unless you're going to pirate it, it's insanely expensive. Probably a bear to configure it properly.
I'd stick FreeNAS into a virtual machine and give it a whirl. If you're wanting to access your files from anywhere on the Internet, it'd simplify matters if you got a Dynamic DNS account set up, so you can access your server with a hostname instead of an IP address. My router supports several different such services, and I use DynDNS.org's. You'll also need to tell your router to port-forward to the fileserver, and you may want to choose a non-standard port to be externally visible, so the scanner bots don't find you.
You'll need to decide which protocol(s) to use to make your stuff accessible, and I can't help you there. It really comes down to what your phone can talk to, since they're less versatile. WebDAV might work. You'll definitely want to run whatever it is over SSL, so people can't sniff your packets.
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