Mac TCP Watcher 2.0 -- Peter Lewis recently released version 2.0 of Mac TCP Watcher, a $10 shareware utility favored by network administrators, power users, and the interminably inquisitive. Mac TCP Watcher exposes the guts of TCP network communications: version 2.0 is compatible with both Open Transport and MacTCP, sports a new traceroute feature, and offers a bundle of other enhancements (including Balloon Help with occasional typos!).
If you're just curious about the paths your packets take between machines on the Internet, you might want to check out Bryan Christianson's freeware program WhatRoute. WhatRoute only works with Open Transport and doesn't offer all the functionality of Mac TCP Watcher, but it can be a handy tool; a beta of version 1.3 offers ping and DNS features. [GD]