We've had a few threads about them too....some enlightening and some down right hysterical.
Here is the short list I could think of on the fly:
FMQ - free motion quilting
WIP - work in progress
PIGS - project in grocery sacks.
Then of course, for fun, someone mentioned the whipped pigs and we kinda digressed from there.
D9P - Disappearing 9 Patch
OBW - One block wonder, like those kaleidescope blocks.
Those are the ones I can think of for now. Hope this helps.