# grep for string
    sed -n '/string/p'

    # double space a file
    cat file.txt | sed G

    # delete trailing whitespace (spaces and tabs)
    cat file.txt | sed 's/[ \t]*$//'  

    # put bar in quotes
    echo "foo bar baz" | sed 's/bar/"&"/'

    # replace spaces with tabs
    sed 's/ /\t/g'

    # replace foo with bar
    sed -i -e 's/foo/bar/' ~/file.txt

    # delete lines matching a pattern
    sed -i -e '/kern/d' /etc/syslog.conf

    # comment out a line (should anchor)
    sed -i -e '/^Something.*/#&/g' /tmp/file.txt

http://www.grymoire.com/Unix/Sed.html

http://www.eng.cam.ac.uk/help/tpl/unix/sed.html

http://sed.sourceforge.net/sed1line.txt