Figuring out distance on an online map

Is there a way to figure out the distance of a circuitous route on an online map such as Google Maps? For example, can I trace out a trail, or several sections of winding road on the satellite view and get the actual distance in anyway? Any other free mapping/satellite programs have this as a feature? Thanks.

The GMaps Pedometer does this.

Sweet! That rocks and is exactly what I was after - thanks SmackFu!

You can also download Google Earth; it has that feature built in.