Knowing the longitude and latitude of a place is very useful – it helps you to map that location exactly in any online map sites like Google maps, Live maps , map quest.
You can get these the co ordinates from Google Maps. Just go to the location you want the co ordinates. Click ‘Link’ or ‘Send’ , located on right side of just above the map. The values that you see after &ll= are the universal co ordinates which can used used anywhere.
Update : iTouchMap.com has a web tool which will do the above internally and provide you the longitude and latitude of any point. try here.