Business clubs

Business clubs with regular meetings (guests usually welcome, often an invitation is required):

American-German Business Club (AGBC)
California Association of Germany (CAOG)
German American Business Association (GABA)
Toastmaster Clubs aim to improve rethorical skills. Munich clubs hold meetings in German, English, German / English, French and Italian
Calando Club
American Chamber of Commerce
Export Club
Anglo-Bavarian Club
Deutsch-Kanadischer Wirtschaftsclub München (German-Canadian Business Club Munich - meets monthly at the Kempinski Vier Jahreszeiten on Maximilianstrasse)
XING Stammtisch München (monthly meetings - see website for details)
Mobile Monday (MoMo)
FIWM Munich IT industry Association with various networking events

These are some online networking groups:

German American Business Association Silicon Valley GABA (search on Yahoo groups, free to join the mailing list)
XING - worldwide online network
LinkedIn - US-based
Ecademy - in February 2005 introduced a paid-only service with a seven-day (only) free trial. Big in the UK, not so big here.
Ryze - worldwide online business network, US based
Meetup.com - worldwide online network for organising real-life meetups, not just business oriented but anything (knitting, bookswapping, etc...)
Munich Network

Other media:

Business

Munich