Curious as to how much traffic your server puts out? MRTG is your friend

I saw and used MRTG back when it was released in 1995. It has come a long way since then. MRTG (Multi Router Traffic Grapher) basically shows you a graph of how much you are outputting via your network, and how much traffic is accessing your server. Yes, INPUT/OUTPUT. Banded together with a statistics package (Webalizer or AWSTATS), this can be a very formidable tool in the weaponchest of a server administrator.
Screenshots of MRTG here.
MRTG-eth.pl is a perl script that can setup MRTG without setting up an SNMP daemon. Too much information? Just go take a look.