Spelling rules in British and American English

There are some spelling differences in American English. In the 1800's, the US Congress actually called for several changes to make words more phonetic. Look at the following examples:

British English American English Examples
words ending in -re change to -er centre - center
metre - meter
words ending in -our change to -or colour - color
words ending in -ogue change to -og catalogue - catalog
words ending in -ise/ize ending only in -ize realise/realize - realize
final -l doubled after short vowel - l not always doubled after a short vowel travelled - traveled
modelling - modeling
words ending in -ence change to -ense defence - defense
licence - license

Thanks to John.