LittleSis is a free database of who-knows-who at the heights of business and government.
Although not strictly a worker's inquiry, this website has good examples of network maps:
We bring transparency to influential social networks by tracking the key relationships of politicians, business leaders, lobbyists, financiers, and their affiliated institutions. We help answer questions such as: Who do the wealthiest Americans donate their money to? Where did White House officials work before they were appointed? Which lobbyists are married to politicians?