When a mac accesses storage not formatted in it's own HFS format, it stores it's additional metadata about the file in another file named the same but starting with "._" It can be annoying and when you're accessing a remote volume that's source control managed with subversion, they show up your status information. This bash shell script will get remove of all ._metadata files residing below the current working directory.

#!/bin/sh
for i in `find . -regex '.*\._.*'`; do rm $i; echo "removing $i"; done

If you save that as "/home/$USER/bin/cleanup" and do a "chmod 777 /home/$USER/bin/cleanup" it will be available next time you open a terminal by just typing "cleanup".