The Norwegian Meteorological Office has put together a time-lapse animation showing the spread of the ash cloud emitted by the Eyjafjallajökull volcano. I’ve converted it from the original animated GIF, which is nearly 14 MB, and uploaded it here. Yellow indicates ash that has fallen by itself, red ash that has fallen as a result of precipitation, and black where the ash cloud is at that moment in time. More information (in Norwegian) here.
Radar Virtuel is a map of European airspace that shows the real-time positions of aircraft; lately it has been showing (1) an overlay of the ash cloud and (2) not many aircraft in the air. For obvious reasons the site has been kind of hard to load lately (or I would have been able to mention it in my previous entry on Eyjafjallajökull). Via Mapperz.