Here is a list of differences
acknowledgement
acknowledgement *, acknowledgment
acknowledgment, acknowledgement
ageing
aging *, ageing *
aging
aeroplane
airplane
airplane
aesthetics
aesthetics
aesthetics, esthetics
aluminium
aluminum
aluminum
among, amongst among *, amongst among
anaemia anemia anemia
anaesthesia
anaesthesia *, anesthesia
anesthesia
analogue analogue analog
analyse analyze *, analyse analyze
annex, annexe annex annex
apologise, apologize
apologize
apologize
archaeology
archaeology *, archeology
archeology, archaeology
artefact artifact artifact
axe
axe
ax, axe
analyse, analyze
analyze *, analyse
analyze
balk, baulk balk balk
banister, bannister banister *, bannister banister
behaviour behaviour *, behavior behavior
behove behoove behoove
blonde (for female) blond *, blonde * blond, blonde
B.Sc. B.Sc. B.S.
burette burette *, buret buret, burette
burnt, burned
burned *, burnt *
burned, burnt
Caesarean Caesarian *, Cesarean, Cesarian Cesarean, Caesarean
calibre calibre caliber
cancelled
cancelled
canceled, cancelled
catalogue
catalogue
catalog(ue)
catalyse catalyze *, catalyse catalyze
centre
centre *, center
center
cheque (noun, money)
cheque
check
chequered
checkered
checkered
chilli, chili chili chili
cigarette cigarette cigarette, cigaret
clamour clamour *, clamor clamor
colour
colour *, color
color
connection, connexion connection connection
cosy
cozy *, cosy
cozy
counsellor
counsellor *, counselor
counselor
criticise, criticize
criticize
criticize
curb (verb) curb curb
defence
defence *, defense
defense
dialogue
dialogue
dialog(ue)
diarrhoea
diarrhea
diarrhea
dietician, dietitian dietitian *, dietician dietician, dietitian
dispatch, despatch dispatch dispatch
doughnut
doughnut
donut, doughnut
Dr (A contracted form of a word, ending with the same letter as the full form, is not followed by a full stop).
Dr.
Dr.
draught (current of air)
draft
draft
dreamt, dreamed
dreamt *, dreamed *
dreamed, dreamt
emphasise
emphasize
emphasize
encyclopedia, encyclopædia encyclopedia encyclopedia
enquiry, inquiry
inquiry *, enquiry
inquiry
enrol
enrol *, enroll
enroll
favour
favour *, favor
favor
flavour flavour *, flavor flavor
fibre
fibre
fiber
flautist
flutist *, flautist
flutist
flavour
flavour *, flavor
flavor
foetus, fetus fetus fetus
forever, for ever forever forever
fulfil
fulfil
fulfill, fulfil
gauge gauge gauge, gage
glamour
glamour *, glamor
glamour, glamor
gonorrhoea gonorrhea gonorrhea
grey
grey
gray
gynaecology gynecology *, gynaecology gynecology
haemorrhage
hemorrhage
hemorrhage
harbour
harbour *, harbor
harbor
harmonise, harmonize harmonize harmonize
haulier
hauler
hauler
homeopathy, homoeopathy homeopathy homeopathy
honour
honour *, honor
honor
humour humour *, humor humor
initialise initialize initialize
jail, gaol jail jail
jewellery
jewellery *, jewelry
jewelry
judgement
judgment *, judgement
judgment
kerb (noun)
curb
curb
kilometre kilometre *, kilometer kilometer
labour
labour *, labor
labor
lasagne lasagna lasagna
leant, leaned
leaned
leaned
learnt, learned
learned *, learnt *
learned
licence (noun) licence license
license (verb) license *, licence license
litre
litre
liter
manoeuvre
manoeuvre *, maneuver
maneuver
marvellous marvellous marvelous
meagre meagre *, meager meager
metre
metre *, meter
meter
mould
mould *, mold
mold
neighbour
neighbour *, neighbor
neighbor
net, nett (amount of money) net net
oedema, edema edema edema
oesophagus, esophagus esophagus esophagus
oestrogen, estrogen estrogen estrogen
offence
offence *, offense
offense
omelette
omelette *, omelet
omelet, omelette
organisation
organization
organization
pædiatrics, pediatrics pediatrics pediatrics
paedophile, pedophile pedophile pedophile
paralyse paralyze *, paralyse paralyze
parlour
parlour *, parlor
parlor
parallelling, parallelled
paralleling *, parallelling, paralleled *, parallelled
paralleling, parallelling, paralleled, parallelled
pedlar, peddler
peddler *, pedlar
peddler
pleaded
pleaded
pleaded, pled
plough
plow *, plough
plow
practise (verb)
practise *, practice
practice
practice (noun)
practice
practice
pretence
pretense *, pretence
pretense
programme, program
program *, programme
program
pyjamas
pyjamas
pajamas
rancour rancour *, rancor rancor
realise, realize
realize
realize
recognise, recognize recognize recognize
rigour rigour *, rigor rigor
saleable saleable saleable, salable
saviour saviour *, savior savior
savour
savour *, savor
savor
sceptical
sceptical *, skeptical
skeptical
skilful
skilful *, skillful
skillful, skilful
smelt, smelled
smelled
smelled
speciality
specialty *, speciality
specialty
sulphur
sulphur *, sulfur
sulfur
theatre
theatre *, theater
theater
theatregoer
theatregoer *, theatergoer
theatergoer
titbit
tidbit
tidbit
towards toward *, towards toward, towards (unusual)
travelling
travelling
traveling, travelling
tyre
tire
tire
vice
vice
vise, vice
vigour vigour *, vigor vigor
wagon, waggon wagon wagon
woollen woollen *, woolen woolen
The first is British, middle is Canadain and the end ones are American spellings......now you know why I make mistakes.
The ones with the asterisk are the most commonly used.
My favorite saying is "That dog don't hunt" Those from the South will know it.