If you are interested in the German region then I think you may need to make your way to Viscom – the “Internationale Fachmesse für visuelle Kommunikation” held in Düsseldorf – 20th to 22nd September 2007.
See http://www.viscom-messe.com/ 
There are some very interesting speakers – especially on the 21st September…
- Digital Signage: Hype oder Trend für die Zukunft?
Thomas Dockter, Dockter Marketing
- Wie wirkt Digital Signage?
Robert Müller, Hochschule für Gestaltung + Kunst
- Michael Schiessel
eye square GmbH
- Christoph Kronhagel
ag4 mediatecture company
- Bernhard Baer
Digitale Medien am POS
- Björn Christiansen
Minicom Advanced Systems
I see that 42mediagroup are nominated for awards with two of their projects at the event as well.