link might be handy : http://www.pfsense.org/ [pfsense.org] good luck!

If you an old pentium III box laying around somewhere you can use it as a firewall/router. stick in 3 network cards, one for your internet connection, one for your local network and one for sharing your internet with. You can cap the speed on the internet sharing NIC, it's seperated completely from your local network. Also make a captive portal so that people will see a webpage where they'll have to click "ok" or something before they can start using your internet. You can put some text up saying you're not some dumbass that doesn't know how to secure his wifi but is actually doing it help the neighborhood and a request to please not abuse the line. I use the shared wifi nic myself too, except i vpn into my local network so i don't have the restrictions. works really great!