Seven British And American Spellings

Some British English (BrE) and American English (AmE) words have the same meaning and pronunciation but different spellings. If you are not sure about a spelling, it's best to look it up in a British or American dictionary as appropriate.
Here are seven common differences:
1. ogue/og
BrE: analogue, catalogue, dialogue
AmE: analog, catalog, dialog
2. our/or
BrE: colour, favourite, honour
AmE: color, favorite, honor
3. ence/ense
Bre: defence, licence
AmE: defense, license
4. s/z
BrE: analyse, criticise, organisation (but z is also used)
AmE: analyze, criticize, organization
5. l/ll
BrE: enrolment, fulfil, skilful
AmE: enrollment, fulfill, skillful
6. re/er
BrE: centre, theatre, metre
AmE: center, theater, meter
7. miscellaneous
BrE: jewellery, programme, practise, pyjamas
AmE: jewelry, program, practice, pajamas
NB1: in BrE program is used when talking about computers
NB2: in BrE practise is a verb and practice is a noun

source http://www.englishclub.com/ref/esl/Power_Of_Seven/Seven_British_And_American_Spellings_2921.htm