I've recently stumbled on a very interesting Lithuanian history compendium until 1795. It is called www.ldkistorija.lt and is only in Lithuanian. Some interesting facts there - for example the Suffolk Duchess Catherine Willaughby lived in a small Samogitian town of Kražiai from 1557 to 1559.
In general, this time period is very interesting to me because it was very pivotal in Lithuanian history. Protestantism, with a powerful Radziwill family (Radvilos) in front was competing against Catholicism with Bona Sforza in front - who also was the Queen of the Polish-Lithuanian Commonwealth. The Catholic religion won, the Raziwills were sidelined, and an even closer union of Lithuania and Poland followed.