These terms were stolen wholesale from the WWW page including the "original" 107 Euphemisms for Masturbation. I've listed here the mostly gender-neutral terms, though there are a few gender-specific terms. There aren't too many here, but they should be enough to keep you busy for a while. For the definitive list of euphemisms, check out this link.

• Doin' the Han Solo
• Doing your homework
• Drilling for oil
• Fastening the chin strap on the helmet of love
• Fire the Surgeon General
• Fishing with dynamite
• Helping put Mr. Kleenex's kids through college
• Holding your own
• Left to your own devices
• Liquidating the inventory
• Making a cash withdrawal
• Minding your own business
• Pat the Robertson
• Playing solitaire
• Putting your thumb in the porridge
• Raining on your parade
• Relishing your hot dog
• Rubbing yourself until you have an orgasm
• Sampling the secret sauce
• Shooting yourself in the foot
• Spending your Christmas bonus
• Stewing in your own juices
• Summoning the genie
• Taking a load off
• Taking matters into your own hands
• Toying with your Death Star
• Using the Force
• Varnishing the banister
• Wrestling with your emotions
• Working up a foamy lather