As said above, Find my friends works quite well if you have a data connection. And you don't have to send your position yourself, your friends/family members can simply ask the app on their device to locate you and it does (again, data connection required).
Another onboard thing is to use the apple maps app, open it, find your location (arrow on the lower left side) and then send (icon upper right corner) that position either via imessage/sms or mail.
The slowest possible method is of course to open the compass app (native as well on the iPhone) and copy the gps position close to the bottom, open mail paste it into a new mail message and send that...