Yud Tes Kislev on Chabad.org
Chabad.org has a wealth of infomation on Knowledgebase subject on Yud Tes Kislev too.
What is Yud Tes Kislev? From our Glossary:
Kislev 19: anniversary of the passing of R. Dovber, the Maggid of Mezritch, in 1772, and anniversary of the release from capital sentence and imprisonment of his disciple, Rabbi Shneur Zalman of Liadi, in 1798; celebrated as a Chassidic holiday amongst Chabad Chassidim
Click here to read more about the Alter Rebbe, Rabbi Shneur Zalman. Check out this biography of the Alter Rebbe with copies of original document and other interesting artifacts.