I quite like the fact that there is no global standard, it makes going abroad more interesting!
The Wikipedia article is extensive and a very good read with some interesting little facts.
For instance, the United States Virgin Islands is the only territory under American jurisdiction that drives on the left (it is a former Danish colony). However despite this almost all its cars are imported from the States and are therefore left-hand drive. It is a popular holiday destination for Americans which accounts for its rather high accident rate!
Sweden changed to driving on the right in 1967, Iceland in 1968 and the most recent right-to-left switch was Burmah in 1970. Conversely, Samoa swapped to
left-hand driving in 2008 and Rwanda and Burandi are debating the same change. The tide is turning!!
~iw