If you don't care about getting all of the Internet's routes then you can use BGP to advertise your routes to the internet and then use static routes with the same metric to route traffic outbound. The static routes will have to point to your serial...
One of the ways that we monitor bandwidth on some of our routers and switches is using MRTG. This is a free tool that uses SNMP to query the devices and dynamically created HTML pages. It is a pretty cool tool and IMHO, really easy to use.Good Luck...