An OpenERP module can be identified by a folder or directory containing the file __openerp__.py

An Ubuntu search for all folders containing that file can be done by running the following command as sudo: (this command also sorts the list by path and outputs the list to a file)

find . -type d -exec test -e "{}/__openerp__.py" ';' -print | sort > modules.txt

You can then open this file in Excel and create a formula to find the last / character in the path and extract just the module name.

=RIGHT(A1,LEN(A1)-FIND("|",SUBSTITUTE(A1,"/","|",LEN(A1)-LEN(SUBSTITUTE(A1,"/","")))))

Once you have the module name, you can sort again just by this column, and you will have a sorted list of all OpenERP module names on the filesystem together with the paths that locate them.