Is there a resource that lists what's outdated in "Stick and Rudder"?
I'm not aware of such a list although I would say 99.99% of this book is not outdated. 

Maybe some of the terminology is outdated when it talks about the "gaits" of the aeroplane for example which is an horse term apparently.

I wouldn't say anything else is though certainly not the concepts, because the air is the same, the laws of physics are the same and human nature the same as it was 70 years ago. Its a very insightful book that should be every pilots reading.

Maybe it goes on more about tail-wheel aircraft and there are fewer of these aeroplanes around today but this only applies on the ground and is still very interesting even for nose dragger pilots like me.