I really like ntop, but there hasn't been a Mac OS X compiled binary available since version 3.2. The package that is available contains the source code, but it takes Xcode and some knowledge of how to make and compile object code for one to be able to make this into a usable product. I don't have the requisite skills (nor do I have the disk space for Apple's Developer Tools), so unless or until someone makes a freely-available binary, this update is only for those who can "roll their own."