This is one of those sites where when I see it I think.
"I should of thought of that"
http://www.mapmyrun.com is the bomb. You can check map out your run and find out exaclty how long it is. This site even includes the elevation levels.
Browsing this site I've found some runs I didn't know about before. Although they could use some better searching tools but I'll work for now.
If you were wondering below is my standard run that I mapped.
