I have never seen the contrail itself from inside. However, on a Delta 757 flight from DTW to ATL, in January, over Ohio at cruise, I did see a spectactular shadow on the cloud below: our plane and a loooooooooong contrail. I did take a picture of it, but I dont have a scanner (that was on film, before I went digital). I'm looking at it now. very cool.
Check out this link. an A321 at probably 35,000 ft, and no contrail! how come?
feel free to check outthe rest of the gallery too