Hi blessedgirl - it obviously depends on the capacity of your flash drive, and just what your purpose is. Do you want the actual project transferred, or do you want to carry a much smaller QuickTime version to play on someone else's computer..or what?
You can Share to CD ROM (which will make a QT file of reasonably small size), but of course any reduction in size also means a reduction in quality. You may just have to experiment. You could also try Share to QT Expert Settings and choose MPEG4 and see what happens to the resulting size.
You can get Flash Drives up to 8GB at least- what size is yours?