Wikimedia Conference 2012/Practical information
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Electricity, Internet, etc 
- 230V at 50 Hz. People from the US, UK, Australia, etc: bring an adapter!
- "Schuko" plugs type F (CEE 7/4), see wikipedia:Schuko
- Cell phone coverage is good pretty much everywhere in Berlin, including subway tunnels.
- Free Wifi is common in Cafes, you may have to ask for a code though.