GmapGIS is an online tool for easy draw on Google Maps. You can use it to draw lines, rectangles, circles or hand-free lines on Google Maps. You can also choose Map Type, add more layers, measure distances, and import / export KML, GeoJSON and CSV Files. Easy to use and useful when you need to visualize or measure an area of territory. Add Label and Markers to enrich maps.
Quick screenshot below:

Online and free to use.