[plug] Finding duplicate files

[Rennie]

On windows I often use an app' called Total Commander which is a file manager 
with a few nifty features.

One that I find most useful is the Find - Duplicate files function. It 
produces a list of all file which are identical, with or without the same 
name, in a given directory and it's sub directories. It´s great for cleaning 
up poorly backed up files/directories.

Does anybody know of an Linux equivalent?

Regards,

Rennie