Say you’d like to find out the IP addresses of lines in your apache access.log (or any log file with a similar format, really) that contain “Googlebot”:

grep 'Googlebot' access.log | cut -d' ' -f1 | sort | uniq

which finds the lines via grep, uses cut to extract the first field (space delimited), sorts the IP addresses and then uniqifies them.

Dirt simple, stupidly powerful.