well, just to let you know. Leopard has this kind of behavior to pick up Shared folder on the network that you are connected to. This happens when i am using my mac with leopard, i tend to browse into other people's folder, without them knowing it. Well, there were around 100 over users that shared their documents on my campus network. I bet they dont even know that i browse their stuff. Oh, i didnt join any workgroup or network. I dont know what happened there.

Just open your finder. There will be one section for Shared besides The Devices, Places and the Search For. You can browse there.

From Finder, Choose Go, then explore from there. either from Computer or Network.