If you would like to be able to click on Google Maps and get exact point-to-point (-to-point-to-point …) distances, do the following.
Go to maps.google.com. In the left column, way down at the bottom, click the link labeled "Maps Labs." You'll get a pop-up. Click the Enable button next to "Distance Measurement Tool." At the bottom of the pop-up, click Save. (screenshot)
You'll now see a tiny ruler icon, just to the left of the distance scale, in the lower left corner of the map. When you want to determine a distance, click that. Then click once on the map at your starting point. Click a second time for your end point (as the crow flies, maybe), or click a series of places, wherever you'd have to turn a corner, say. (screenshot)
Click the little ruler icon again to make the distance tool stop. Click the Maps Labs feature again if you want to disable it.
Happy map nerding!
I really like the Delete Last Point feature, which can be clicked repeatedly, if you'd like to backtrack.
I haven't yet remembered to get out my 100-foot tape measure to see how accurate this tool is, but some day, when it's dry . . .