The Panama Canal
The path that a boat would travel through the Panama Canal has been drawn in red. Technically, only the bottom 1/3 is the actual canal. The rest is just rivers and lakes.
http://www.quikmaps.com/
http://www.quikmaps.com/
Analysis: I like QuikMaps for drawing on Google Images. Text can be added as well (see the "Panama Canal" label). This will be good for Geography, Watery Earth, Current Events, and maybe even Mystery Skypes.