Here is one that I used to remember resistor color code:
Bad Boys Ravage Only Young Girls But Violet Gives Willingly.
Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White

hmm... i have one in french for the coordination complements...
Mais où est donc Ornicar? (But so where is Orniar?)
for mais(but) - ou(or) - et(and) - donc(so) - or(whereas) - ni(niether) - car(because)

interesting...i think the only one i have is never eat shreded wheat and BEDMAS. never (north) eat (east) shreded (south) wheat (west) B (brackets) E (forgot name...) D(devide) M (multiply) A (add) S (subtract) yah these things help me pass stuff

Nice ones. I made up a few memorable ones, but my biggest feat was one that allowed me to memorize all the 20 amino acids, ordered into their main groups (Polar hydrophobic,non polar etc).
It's rather personal, so I won't give it here, but after this, all I had to do to pass Cell Biol's first midterm was to memorize the structures of all the acids. Sadly, I wound up with a below median score as I messed 1 R group up by using the structure from another textbook.
How those premeds manage that easily is beyond me. (And they go on to memorize everything in organic chem!)

Roy G Biv = colors of the rainbow

Hmmm...

Nooit Opstaan Zonder Wekker. (Never rise without alarmclock)
Nooit Oorlog Zonder Wapen. (Never war without weapon)
N: Noord (North)
O: Oost (East)
Z: Zuid (South)
W: West (West)

I could never get those in the right order. And I remembered the order of the colors of the rainbow, and the colors, by an old kiddy song I performed once with my 'girl scout' group.

er..you all LOST ME!

Mnemonic devices are words or sentences that have a certain 'code' in them, people make them to learn certain things easier. It's just like making a song of some things, it's just an easy aiding tool.

that it is. it also help on remembering names aswell.
Rolls of bread = Rolzin.

Jokes help me remember things.

Like a Freudian slip... when you say one thing and mean a mother.