Who's connected to my Mac?

I've asked this question before. I never got a reply for anyone, and I've never been able to identify a way to do it myself.

Sorry.

It won't tell you exactly who is connected, but 'netstat' may show an IP address. For example, to see the IP addresses of computers connected over afp, try entering this in "/Applications" > "Utilities" > "Terminal.app":<pre>netstat -an | grep \.548.*ESTABLISHED</pre>Though there may be other ways, to actually figure out which account is being accessed, it may be necessary to have had "activity logging" enabled (I think by default, only "error logging" is enabled). For ssh, use "22" instead of "548" in the 'netstat' command, and the login record could be viewed with eg 'last'...

I think also...
netstat -na | grep 548
without the rest will tell you also as mentioned, the 'last' command...
last -50 | grep still

If you have Airport Base Station, then AirPort Monitor Utility gives lors of info.
http://www.versiontracker.com/dyn/moreinfo/macosx/22129

You can glean much from Network Utility>Netstat & Appletalk, but for Heavy Duty detection/warnings you can use HenWen...
http://www.apple.com/downloads/macosx/networking_security/henwen.html

Where do I look to know who's connected to my Mac over the ethernet network? Something so simple, but I can't find it.

You are probably wanting to see which users are logging in using apple filesharing. You can use xAFP to monitor this.

To see which users have been login into your mac via ssh or physically infront of your mac open your terminal and use the following command.

last