Webtrace.info - Traceroute on steroids
There are a lot of traceroute programs out there. This one called WinMTR was recently recommended by Akamai support during one of the troubleshooting sessions. Its based of another Linux tool called mtr (Matt's traceroute) which is another one I had never heard off.
I liked it so much, that ended up making an enhanced web interface to it. Check it out here at Webtrace.info.
Webtrace provides extra networking information which is really helpful for folks who are trying to investigate networking issues. There are a lot of hyper links which allows them to quickly drill down into issues (like who is loosing packets).