Here is a good starting point. From Dave Casdorph's website.
http://dgcasdor.ipower.com/sitebuildercontent/sitebuilderfiles/2000-2019a.pdfWon't necessarily tell you if a particular car is brand new, but that data can be extrapolated. (there's also a 1990-1999 list I believe)
What I think...
-New(er) frac sand cars
-New(er) iteration of Ortner "porches" hopper
-New open-grid version of a Maxi-I stack car
-New 65ft Gons (the newer TTX style)
-Higher capacity 5161-style covered hopper
-New design 5-bay aluminum coal hopper
-A couple of new autorack designs
-Brand new carbon black covered hoppers