A brief post to sing the praises of this website (run by Michal Derela) devoted to Polish armoured formations 1918-1939, including armoured trains. For those interested in wargaming the 1939 Polish campaign the information contained on the site is invaluable. It is written entirely in English which makes it (as far as I can tell) a unique source.
Anyone interested in Polish military history of the 20th Century should check out this site. A link is posted (under 'Polish Military Site') to the left of this post.