I really like Cisco's 'Network Magic' software; but the site says they no longer support Mac.. Does anyone know of any software like it, that is supported on Mac?
Well, there are some network monitoring & management tools for Mac OS X you may want to have a look at (although I haven't found a direct hit I guess). For example,
To see who is on your network you may use Ntop.
Since Mac OS X is a Unix-based operating system, there are also command line tools that allow you to manage other Macs remotely via SSH. For example,
And, last but not least (as already pointed out by mrbitch), there is quite some 'Network Magic' functionality that ships with Mac OS X by default (see, for example, the 'Sharing' system preference pane).