The Minor Prophets: Habakkuk - Historical and spiritual overview of the Biblical prophet. - http://www.zianet.com/maxey/Proph7.htm
The Prophet Habakkuk - Rabbinic traditions about the prophet, including his apocryphal interactions with Daniel in the lions' den. - http://www.chabadonline.com/shavuot/shavuot-article-page.asp?ArticleID=2054
Book of Chabakuk - The text of the Biblical chapters in Hebrew and English. - http://www.hareidi.org/bible/Habakkuk.htm
Habakkuk - Profile of the prophet from a joint Lutheran and Catholic bible study project. - http://www.aboutbibleprophecy.com/p17.htm
Catholic Encyclopedia: Habacuc (Habakkuk) - Commentary on the Biblical prophet from the traditional Catholic perspective. - http://www.newadvent.org/cathen/07097a.htm
Jewish Encyclopedia: Habakkuk - Overview of the prophet from the traditional Jewish perspective, including rabbinic commentary. - http://www.jewishencyclopedia.com/view.jsp?artid=7&letter=H