I before E (yuccamuffin.com)

<?php

    $words = file('/usr/share/dict/words');
    $words = array_map('trim', $words);

    // Ignore words with any punctuation
    $words = array_filter($words, 'ctype_alpha');

    foreach($words as $word)
    {
        // ignore proper nouns (they start with an uppercase letter)
        if(ctype_upper($word[0]))
        {
            continue;
        }

        if(preg_match("#[^c]ei#", $word) === 1)
        {
            echo "$word\n";
        }
    }

?>

absenteeism
ageing
ageings
ageism
agreeing
albeit
anteing
apartheid
atheism
atheist
atheistic
atheists
aweigh
bantamweight
bantamweights
beige
being
beings
bingeing
birdieing
blueing
boogieing
caffeine
canoeist
canoeists
casein
clueing
codeine
counterfeit
counterfeited
counterfeiter
counterfeiters
counterfeiting
counterfeits
counterweight
counterweights
cueing
cuneiform
decaffeinate
decaffeinated
decaffeinates
decaffeinating
decreeing
deice
deiced
deicer
deicers
deices
deicing
deification
deified
deifies
deify
deifying
deign
deigned
deigning
deigns
deism
deities
deity
dieing
disagreeing
dyeing
edelweiss
emceeing
facsimileing
featherweight
featherweights
feign
feigned
feigning
feigns
feint
feinted
feinting
feints
feistier
feistiest
feisty
filigreeing
flambeing
fleeing
flyweight
flyweights
foreign
foreigner
foreigners
foreseeing
forfeit
forfeited
forfeiting
forfeits
forfeiture
freeing
freight
freighted
freighter
freighters
freighting
freights
fricasseeing
garnisheeing
geeing
geisha
geishas
gesundheit
glueing
gneiss
guaranteeing
heavyweight
heavyweights
heifer
heifers
height
heighten
heightened
heightening
heightens
heights
heinous
heinously
heinousness
heir
heiress
heiresses
heirloom
heirlooms
heirs
heist
heisted
heisting
heists
herein
heterogeneity
hieing
hoeing
homogeneity
horseshoeing
hundredweight
hundredweights
inveigh
inveighed
inveighing
inveighs
inveigle
inveigled
inveigles
inveigling
kaleidoscope
kaleidoscopes
kaleidoscopic
kneeing
lei
leis
leisure
leisurely
leitmotif
leitmotifs
lightweight
lightweights
middleweight
middleweights
monotheism
monotheist
monotheistic
monotheists
neigh
neighbor
neighbored
neighborhood
neighborhoods
neighboring
neighborliness
neighborly
neighbors
neighed
neighing
neighs
neither
nonpareil
nonpareils
nuclei
nucleic
obeisance
obeisances
obeisant
onomatopoeia
onomatopoeic
outweigh
outweighed
outweighing
outweighs
overseeing
overweight
pantheism
pantheist
pantheistic
pantheists
paperweight
paperweights
peeing
pennyweight
pennyweights
pharmacopoeia
pharmacopoeias
pieing
plebeian
plebeians
poltergeist
poltergeists
polytheism
polytheist
polytheistic
polytheists
protein
proteins
pureeing
queueing
refereeing
reign
reigned
reigning
reigns
reimburse
reimbursed
reimbursement
reimbursements
reimburses
reimbursing
reimpose
reimposed
reimposes
reimposing
rein
reincarnate
reincarnated
reincarnates
reincarnating
reincarnation
reincarnations
reindeer
reindeers
reined
reinforce
reinforced
reinforcement
reinforcements
reinforces
reinforcing
reining
reinitialize
reinitialized
reins
reinsert
reinserted
reinserting
reinserts
reinstate
reinstated
reinstatement
reinstates
reinstating
reinterpret
reinterpretation
reinterpretations
reinterpreted
reinterpreting
reinterprets
reinvent
reinvented
reinventing
reinvents
reinvest
reinvested
reinvesting
reinvests
reissue
reissued
reissues
reissuing
reiterate
reiterated
reiterates
reiterating
reiteration
reiterations
reparteeing
reveille
seeing
seeings
segueing
seismic
seismically
seismograph
seismographic
seismographs
seismologist
seismologists
seismology
seize
seized
seizes
seizing
seizure
seizures
sheik
sheikdom
sheikdoms
sheikh
sheikhs
sheiks
shoeing
sightseeing
singeing
skein
skeined
skeining
skeins
sleigh
sleighed
sleighing
sleighs
snowshoeing
sortieing
sovereign
sovereigns
sovereignty
spontaneity
spreeing
squeegeeing
stein
steined
steining
steins
stymieing
surfeit
surfeited
surfeiting
surfeits
surveillance
teeing
theeing
their
theirs
theism
theist
theistic
theists
therein
throeing
tieing
tingeing
tiptoeing
toeing
treeing
trueing
twingeing
underweight
unfeigned
unseeing
unveil
unveiled
unveiling
unveils
vagueing
veil
veiled
veiling
veils
vein
veined
veining
veins
villein
villeins
vogueing
weeing
weigh
weighed
weighing
weighs
weight
weighted
weightier
weightiest
weightiness
weighting
weightless
weightlessness
weightlifter
weightlifters
weightlifting
weights
weighty
weir
weird
weirded
weirder
weirdest
weirding
weirdly
weirdness
weirdo
weirdos
weirds
weired
weiring
weirs
welterweight
welterweights
wherein