There are many reasons you may want to set up a small server of yours and shares files with friend and family. There are many solutions as well. But most of them are robust, huge in bulk (for example, Apache) and need professional configuration. Try Lighttpd. It is literally feather-light, has multiple mods like HTTP, webdav, magnet etc.
To install on Ubuntu, run:
$ sudo apt-get install lighttpd
Here’s a quick configuration guide for starters.
If not sure, how one can access your server over the internet, run:
# curl ifconfig.me
or check it from http://www.whatismyip.com/. A remote user can now browse your server with the IP you see.