50mm "Normal" Lens... Ok, but "Normal" on FF or APS-C Sensor?

Thanks for all of the replies, very informative!

I was a little surprised to learn that some "normal" focal lengths extend that far on the tele end. I use a Sigma DP2 which is a fixed 41mm lens (FF equiv) and it always seemed just about right as compared to what my eyes see. Very interesting.