Performance Monitor (perfmon) can capture this data into a SQL Server database and create graphs for you.
You can also use <a href=”http://oss.oetiker.ch/mrtg/”>mrtg</a>. It installs on a *nix server and can pull the data via smnp.
You can also use <a href=”http://cricket.sourceforge.net/”>Cricket </a>to monitor and graph this data as well. It also installs on *nix (but can be done on Windows with a little work).