Put a media server on it such as Plex and stream from it.
Put some shares on it and use it as a file server/backup destination
Or put a second drive in it and create a RAID 1 with free nas, and then put shares on it. Install ubuntu and run an apache webserver.
If you're not a linux guy just use XAMMP and then run a webserver.
Setup a torrenting box (utorrent, deluge both have webserver capabilities)
Add a NIC and install PFSense to turn it into a router
Or, better than any of that, plug an access point into it and do this