For the ladies:

a date with Charlie
bean rubbing
brooking
buffin' the muffin
buttering up the whisker-biscuit
churn the butter
Clinton's cave
composing on the single-key piano
dancing with Damien
date with Rosie
diddle
dildo oneself
double-click your mouse
digging a trench
driving Miss Daisy
feed the other mouth
feed the cannibal
fiddle
finding Nemo
finger-bang
finger oneself
finger-fuck oneself
five finger taco tango
flicking Flinkman
flick the budgie (Australia)
flicking the bean
four-lipped whistling
frig
frosting the muffin of love
giving the fuzzy bunny a carrot
gusset typing
itchin' the ditch
impeaching Bush
jill off
harvesting lentil
letting your fingers do the walking
let the beaver swim
little Southern romance
making soup
massaging the mound
marching the penguin
nursing the hatchet wound
paddling her canoe
playing Sonic
playing the pelvic piano
Hand Solo
plunging the Happy Hole (US)
poke oneself (Britain)