A FEW POPULAR ANSWERS (there are several others):
BACKSTROKE, BIRTHPLACE, BREASTSTROKE, CORKSCREW, DOWNSTREAM, DUMBSTRUCK, EARTHSHAKING, ERSTWHILE, FILMSTRIP, HANDSPRING, JOCKSTRAP, LENGTHWISE, MATCHSTICK, NIGHTSHIRT, NIGHTSPOT, OFFSPRING, PITCHBLENDE, SONGSTRESS, SPENDTHRIFT, SPORTSWRITER, SWITCHBLADE, THUMBSCREW, WITCHCRAFT.
Strengths, Catchphrase (6 consonants)
posted by Adam on 2-9-2010 at 7:40 am
STRENGTHS. Which has the advantage of not being a [quasi-]compound word.
posted by Hugh on 2-9-2010 at 7:50 am
Does ‘lunchbreak’ count? I doubt that’s an official word but it sure is a commonly used phrase.
posted by Blaine on 2-9-2010 at 7:55 am
Angstrom and birthplace
posted by Michelle on 2-9-2010 at 8:09 am
blaCKSTRap
joCKSTRap
posted by Doc Rock on 2-9-2010 at 8:24 am
ERSTWHILE
posted by Rus on 2-9-2010 at 8:29 am
lengths
posted by Katie on 2-9-2010 at 8:35 am
Twelfths.
posted by Matthew E on 2-9-2010 at 8:44 am
phenoLPHTHalein-it’s an acid/base indicator
posted by Nick on 2-9-2010 at 8:45 am
oFFSPRing
posted by Ryan on 2-9-2010 at 8:45 am
ThousaNDTHS
posted by Chris on 2-9-2010 at 8:47 am
witchcraft…
posted by Alex B on 2-9-2010 at 8:54 am
nightstick
posted by JD on 2-9-2010 at 9:00 am
switchblade
posted by Bryan on 2-9-2010 at 9:00 am
corkscrew
posted by KevinGA on 2-9-2010 at 9:03 am
The gate to our backyard has a laTCHSTRing, and the factoid about it having six consecutive consonants appeared at a local spelling bee just a few days ago.
posted by Trivia Why's Guy on 2-9-2010 at 9:11 am
syzygy
posted by k on 2-9-2010 at 9:27 am
Hardscrabble
posted by Shawn on 2-9-2010 at 9:46 am
Worthwhile
posted by Kevin on 2-9-2010 at 10:10 am
SYNCHRonize …. 6.
posted by Munnster11 on 2-9-2010 at 10:50 am
heaRTSTRings
posted by Doc Rock on 2-9-2010 at 10:53 am
heaRTHSTone
posted by Tracy on 2-9-2010 at 11:15 am
EIGHTHS
posted by giles on 2-9-2010 at 11:23 am
The real trick is finding one that is not a compound word, pluralization, or using y as a vowel. Not that I’ve been able to do it, but I’m trying!
posted by Rob on 2-9-2010 at 12:27 pm
crwth
posted by Matt on 2-9-2010 at 12:39 pm
So far, 20% of the repondents didn’t follow the instructions.
I wonder if that’s average for any task for which instructions are given?
posted by B on 2-9-2010 at 12:56 pm
Downstream?
B … the math puzzles go the same way. Usually about the 5th or 6th comment is from some yayhoo with another answer that either doesn’t use digits 1 through 9 or doesn’t follow the rules of arithmetic … which is all explained in the directions.
posted by Dinosaur on 2-9-2010 at 1:44 pm
BORSCHT! I know, foreign word, but it’s part of the English language now.
posted by Mark on 2-9-2010 at 2:01 pm
Angsts
posted by Sharon on 2-9-2010 at 2:09 pm
matchstick
posted by Dani on 2-9-2010 at 2:27 pm
lengthwise
posted by Ed on 2-9-2010 at 3:09 pm
Highstrung
Eighthstreet? (7 consonants)
posted by Jeffrey on 2-9-2010 at 3:14 pm
niGHTSHade (the deadly flower)
reCaptcha: Mr depleted
posted by PartiallyDeflected on 2-9-2010 at 3:30 pm
How about “Perthshire?”
posted by Jason G on 2-9-2010 at 5:26 pm
aSYMPTote, a favorite of my math teacher because there are five consonants in a row. It’s some sort of graph term about going to infinity…it was awhile ago.
posted by Jen on 2-9-2010 at 6:40 pm
niGHTSHade
posted by Melissima on 2-9-2010 at 8:23 pm
Earthshine — which illuminated the astronauts.
posted by John Land on 2-9-2010 at 9:27 pm
wellspring
posted by Rathwel on 2-9-2010 at 10:06 pm
crwth
posted by First Post on 2-9-2010 at 10:32 pm
suBMISSible
ReCaptcha: knead or
posted by Lain on 2-9-2010 at 11:57 pm
Tetragrammaton
posted by Chucklz on 2-10-2010 at 12:10 am
breaststroke
posted by TV on 2-10-2010 at 3:56 am
ooh there are lots but my favourite would probably be muckspreader
posted by zy on 2-10-2010 at 6:36 am
Lightswitch
posted by Betsy on 2-11-2010 at 11:05 am
aRMSTRong I know it’s a proper name, but I figure it’s a common enough surname.
posted by Mishael on 2-11-2010 at 1:04 pm
zyzyx – like zyzyx road
posted by kelly on 2-11-2010 at 6:58 pm
sanskrit
posted by yayer on 2-17-2010 at 10:19 pm
nightclub
posted by rd on 3-9-2010 at 4:45 pm
CaTCHPHRase… 6 consonants, and I believe it is now a single word
posted by Rick on 6-25-2010 at 11:14 pm