Depending on your Backup Method...

1)These files are backed up when you backup the tablespace that contains them.

2)If you do an export (exp command) you can backup your stored procedures.

3)MY method like Marks is to save a text file that I used to create the stored procedures.

You can get all you stored procedures out of the Database by...
select 'CREATE OR REPLACE '||name||' AS '||text from user_objects
where type='PROCEDURE';

You could spool this to a file and you would have the text for the stored procedures...(remeber to save the name....)

HTH