Mounting/Unmounting USB Drives

A quick question about USB drives. When I insert and mount a USB stick I can effectively read and write data but when I unmount it the LED on the stick doesn't go out, so when I remove the stick the USB port is not re-initialised when I try to re-insert it. So the only way I can get the box to read the stick again is by doing a reboot. Is there a way to unmount it so that I don't have to reboot  every time?