By Fire and Sword is a new set of rules for 17th Century warfare in Eastern Europe (http://www.fireandsword.wargamer.pl/index.php). The good news is the rules are out and they look fantastic! The bad news is they are only available in Polish. The good news is also they will be released in English in May of 2012. Excellent! The period is nicely covered in a number of historical fiction novels (The Deluge, With Fire and Sword, etc.) by Henryk Sienkiewicz.
Here's a three part review from the excellent Blog Anatoli's Game Room:
Part One: (http://anatolisgameroom.blogspot.com/2011/12/with-fire-and-sword-rules-review-part-1.html)
Finally, there is a dedicated set of rules to cover Winged Hussars; Janissaries; Cossacks; Boyars, etc. where they are not just an after thought tacked onto a Renaissance warfare set of rules. Now, where did I put my Poles?
Oh, and if your are interested in the period, North Star carries the publisher's 15mm figure line (http://www.northstarfigures.com/list.php?man=108&page=1).