I'd first try disabling all sharing options in Prefs. Then look at your network adapters for any connection that looks out of place (like an adapter that shouldn't exist).
I'd also drop to a terminal and issue an "ifconfig" and just make sure all the network adapters shown there are represented in the network settings prefs. If there's an extra adapter, manually try removing it by issuing a "sudo ifconfig delete [interface name]" command.
Also, turn off ipv6 support if you're not using it (it's likely you're not).
When that's all done with, reboot, and see if the networks still show. It's possible that your network actually shares a local community network (like if you live in an apartment building), and these networks could just others Macs in your local network.
It's interesting that one of the networks contains the work "panther," as the first and last time any Mac I've owned got hacked was running Panther... which begs the question as to what OS you're running.
If you're connecting your Mac straight into a cable modem (or the wall via ethernet), you might consider getting an access point or better yet an Airport (or Airport express). Connecting to the Internet via an access point adds connection abstraction and considerable security will almost no effort.
More details about your network would be helpful, and you might even try calling your ISP and asking their tech support to look into it.
Good luck.