Here is one I learned in fire class the other day:
Atmospheres you need to wear your SCBA in (TOES):
T - Toxic
O- Oxygen deficient
E- Elevated Temperatures
S- Smoke
The spectral classes of stars (hottest to coldest):
Oh, Be A Fine Girl, Kiss Me!
The one I used to use that I haven’t seen on here.
SEPARATE: Never separate a para from his parachute
My favourite mnemonic for the planets is:
My very easy method just shows us nine planets.
Planets is : My Very Easy Method Just Speeds Up Naming Planets
Trig. : Silly Old Harry, Caught A Herring, Trawling Off Afganistan.
and there was also: OIL RIG, Oxidation Is Loss, Reduction Is Gain, but that isn’t a mnemonic.
A guy was showing my photography club his color darkroom, and he said the the mnemonic he used for remembering the order of colors on the color wheel (Blue, Magenta, Red, Yellow, Green, Cyan) was
Bad Men Rape Young Girls Constantly
For the order of sharps on the staff, I was taught
Fat Cats Go Down Alleys Eating Birds
friedo, In June 1995 I received a closed-head injury (brain damage) in an automobile accident. It would be almost three years before I learned the multiplication table and multiply again. But I knew all about Chief SOHCAHTOA almost immediately after I awoke from the coma. 
Mine is a poem.
Thirty days hath September,
April, June, and November.
All the rest have thirty-one
Save February, which is totally screwed up and doesn’t rhyme.
Great Spain?! How do you ever remember that? King Phillip Came Over For Great Sex, man.
The version of the resistor color code I heard: Black Bart Rides Over Your Grave Blasting Violent Guns Wildly
I like the Wild West mental imagery on that one.
Elements of the justified use of deadly force against an assailant: Administration Of Justice (stands for “ability, opportunity, and jeopardy” of the assailant to pose a deadly threat to you)
A Rat In The House Might Eat The Ice Cream.
This still goes through my head when I’m confronted with the need to spell arithmetic.
For sharps:
Father Charlie Goes Down And Ends Battle
And it works in reverse for flats:
Battle Ends And Down Goes Charlie’s Father
And for the order of operations:
Please Excuse M’Dear Aunt Sally
(To keep us from using addition before subtraction or something, she wrote it on the board like this before teaching us:
P
E
M D
A S
)
You’ll love this one.
http://users.aol.com/s6sj7gt/mikerav.htm
And it goes on for another seventeen verses.
I Have No Bright Or Clever Friends…Iodine, Hydrogen, Bromine, Oxygen, Chlorine, Fluorine
All the diatomic molecules…although I have to remember that the mnemonic is FOR diatomic molecules before I can remember the mnemonic! I haven’t used it since grade 9…7 years ago.
Oh, can anyone fill this out? Periodic table of the elements, my father used to quote it but I’ve forgotten half of it:
Row 1: Hydrogen - helium - nothing
Final Column - noble gases - there was one, I don’t recall it; but it’s important as they’re left out of the row ones.
Row 2: Little Boys Buy Coco Nuts on Fridays (Li Be B C N O F)
Row 3: Naughty Margaret Always Says “Pass the Sugar Claude” (Na Mg Al Si P S Cl)
Row 4: Karl Can Scan Tiny Verses something something…
I don’t think it went much further. Not into the Lanthanides anyway.
The order of the modes of the major scale: I Don’t Play Like My Aunt Loky.
(Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, Locrian)
The twelve cranial nerves:
On old Olympus’ towering top, a fat armed* girl vends snowy hops.
*[sub]alternate versions exist[/sub]
I always remembered this one simply by pronouncing the whole line (including argon): namgal sipsclar.
Heehee, “keep us from using addition before subtraction, …or something”?? But I bet you know how to do the math!!
Okay here’s something funny, I’m a mathphobe, but I remember what these all mean JUST because of the PEMDAS.
Parenthesis first, then exponents, then mulitiplication, then division, then addition and subtraction.
I think there are some more complicated ones too, but I don’t remember them right offhand.
My current favorite is “Star right, Star Bright” to help remember Starboard is on the right hand of the ship.
OK, here are my favorites (that have not been named, or were quoted differently)
Classification: “Phoenix College’s Ornery Foxes Go Slowly” (although I made that one up, I liked the King Philip one better)
Bones of the wrist: “Never Lower Tillie’s Pants, Mother Might Come Home”
Cranial nerves: “On Old Olympus’ Towering Tops, a French And German Viewed Some Hops” (But the Auditory nerve is now called the vestibulocochlear, so that messes it up, unless you remember that one)
My son’s own mnemonic for lines on the bass clef: “George Buys Dead Farm Animals”
And nobody has exactly quoted the Planet one I learned Lo these many years ago in Philly: “Martha’s Violet Eyes Make John Stay Up Nights Period.” I suspect that the mnemonic predates the discovery of Pluto, hence the period.