Tom McDonnell: The New York Times has put up a useful visualisation charting potential channels of contagion within the Euro zone.
For a nice visual time series of European debt and deficit levels see here. The blooming of debt post 2007 is very stark.
The Guardian has an interesting visualisation showing how a Greek restructuring compares to historical restructurings here. The button in the top right of the chart shows how countries have fared post restructuring.