Calculating the mileage of your training session.

It does not matter if you are cycling, running, walking or footbiking, it's always good to know the mileage you have just accomplished.
I know that a GPS device does the trick (I'm a big fan of my Garmin Etrex H) but sometimes you want to have free hands or you just don't have your device with you.
If you are used to run/cycle/walk in an urban environment you should bookmark this site:
http://www.geodistance.com/
It's the best and quickest way to know the exact numbers of kilometers or miles you have covered in your training session. You just have to draw the route on the map.
It can be very helpful to calculate the step lenght if you use a pedometer (just divide the mileage for the number of steps).
Some time ago there was another site (mapmyrun) doing the same service, but now it requires registration.
 Geodistance.com is more straight-to-the-point, you just insert the name of the street (and city) where your training session started and you are ready to draw the route.