Automated Attachments?

["Adam Williams" <awilliam@xxxxxxxxxxxxx>]

Does anyone know of a package that lets one specify and e-mail attachment at
the command line.  For  cron jobs and such I frequently do a 'cat {file} | mail
-s 'Subject' who@where'.  But know I need to automatically send a file as an
attachment in a e-mail message,  the file is a fixed record length data file
containing "electronic invoicing" information to another company.  I've looked
around with apropos and the LSM but haven't found anything that clearly states
it can do that.  Although metamail and such seem to hint that they can I
haven't been able to understand much from their man pages.