From here.
Helmets
Malta - Mandatory for all cyclists since 2004
Sweden, Slovenia and Czech Republic - Mandatory for under 15s (in Sweden since 2005 with no move yet for it to be madnatory for all)
Spain - Mandatory outside urban areas, except (seriously) when going uphill...
Passengers
France - You can only carry a passenger in France if he/she is under 14 and the cyclist is over 16.
Primary
Germany - In designated 'Bicycle Streets' cyclists can use the whole of the road and drivers must wait behind a cyclist.
Bike Lanes
Germany, and some of Scandinavia - Bike lanes must be used by cyclists if they are of sufficient quality.
Cycling Age
Switzerland - Child must be of school age before being allowed to cycle on the road
Denmark - Under 6 not allowed to cycle on the streets nuless accompanied by someone over 15
Germany - Same as Denmark, except it's under 8 rather than 6.
Poland - Only allowed on the road if over ten and have passed a test.