I needed to move one of my VirtualBox setups to another computer but the disk image was huge and wouldn’t fit on my thumbdrive. Digging around in the VirtualBox settings I noticed an import/export function.
The original disk image was 4.13GB. Exporting it resulted in two files that totalled 1.75GB! That will easily fit on my 2GB thumbdrive (or Dropbox).
Exporting (and importing) is a straighforward process. Select export - you will be given the opportunity to define some configuration values for your machine, then simply define the export filename. Import is the reverse - select import - location you exported file and proceed. Exporting my 4GB disk took about 25-30 minutes.