If you're a networking geek (and I know some of you are), you may be interested in this deal from WildPackets (Mahboud's company) for EtherPeek in all of its various flavors. Now, for $99 you can get a pretty darned nice packet decoder and capture product with a GUI.

True, they haven't been putting nearly as much effort into the Mac product as the Windows one as of late, but I just checked and the demo still works under Tiger, so I'm guessing it isn't just a swansong sale for the Mac version before Tiger releases. Who knows, if people fork over the hundred bucks, WildPackets may see the benefit of continuing to support the Mac.