If one compares US and British usage, one finds apparently contrasting expressions which mean the same thing, for instance: to fill in a form versus to fill out a form. We offer an explanation and other interesting examples of how two nations are “divided by a common language”.
Vocabulary guide BE/AE
In the UK, they drive slowly over sleeping policemen. Check out why in this vocabulary guide.
Grammar guide BE/AE
About.com made an short overview about grammar differences between American and British English
American and British English differences - Wikipedia
Wikipedia has a scientific overview about differences between American and British English