There are a <a href="http://www.slac.stanford.edu/xorg/nmtf/nmtf-tools.html">HUGE number of network
monitoring tools</a> with all kinds of variations.  Some of the ones I've run across that I've liked
include:

<ul>
<li>Wireshark's <A href="http://www.wireshark.org/docs/wsug_html_chunked/ChStatistics.html">statistics</a>
<li><a href="http://pf.itd.nrl.navy.mil/protools/trpr.html">trpr</a> - TRace Plot Real-time
<li>"dashboard" style
    <ul>
    <li><a href="http://www.mikrotik.com/thedude.php">The Dude</a> &mdash; can do ping/tcp-ping/http/SNMP
    </ul>
</ul>