To save percious 20MB on the internal Flash of your Nokia N810, Nokia N800(Maemo Operating System) for installation applications and even more, I copied certain files and directories to my External 8GB Memory Card.
The folders that you can move and don't break the boot of your Nokia N800, N810 (Maemo Based) platform are listed
9) Please notice that there are alot of hidden files/folders in your home directory , if you move them that will break the GUI
You can delete un-needed language files on /usr/share/locale
Files that if you MOVE WILL BREAK YOUR BOOT are
You may ask why moving certain folders/files on Maemo platform will break your boot, because simply it does not mount the external flash on the boot sequence
VERY IMPORTANT NOTE : you need to format you memory card as ext2 fileystem to be able to preserve file permissions as the default file system of those cards are vfat