Try running:-
du -hxP <dir> | grep '[0-9]M'
to find files and folders that have a size in Megabytes. It will take a long time to run. The x
option makes it stay on one file system (so that it doesn't try to add up /proc for example) therefore you'll need to run it against the mount point of each mounted partition that you wish to check.
Run it as root
in order to get a more accurate result.
Note: It'll take a while to run!