If, like me, you want to create some polylines or polygons on a Google Map then it can be quite laborious to have to find the latitude and longitude of the next point, add it to the code and so on. This page simplifies the process somewhat. Just click on the map (or type your lat/longs into the 'Text input' tab) and the Javascript code and KML required will be generated for you on the Code and KML tabs. You can remove your last point or clear the whole thing by clicking the relevant buttons. You can also drag points around using the red circles on points
Type in your input latitude/longitude pairs and press the button. Each lat/long pair should be separated by a comma or tab and each lat/long pair should be on a new line