Success - Double the c and double the s and you will always have success!

Together - To get together, you have to get her!

Friend - A friend is a friend 'til the end!

I still use those from time to time. There is also the Right Hand Rule. Helpful determining the direction of the magnetic field created by a moving current (or something). Is it really a mnemonic device if you don't remember the details?

I also am sure you, Wordwind, as a music teacher of youngsters, know all the Every Good Boy Does Fine, FACE, All Cows Eat Grass, etc. mnemonics for learning the notes of the staff.