Tisha B'av Resources - Features three PDFs dealing with customs and observances, text study of a mishnah in Masechet Taanit, and a Midrash of Megilat Eichah. - http://www.hillel.org/jewish/holidays/tishabav/
Story of Kamsa and Bar Kamsa - The classic story that gives the reason behind the destruction of the second Temple. - http://www.jewishmag.com/12MAG/KAMSA/kamsa.htm
Tisha B'Av and The Three Weeks - Laws and rituals, essays, poetry, and Talmudic insights on this period of mourning. From Ohr Somayach yeshiva in Jerusalem. - http://ohr.edu/yhiy.php/holidays/tisha_bav/
Tisha Bav And The Three Weeks - Take a detailed tour of the Holy Temple, and discover how to observe this time of mourning. Includes history, current calendar, practical "How To" guide and insights into the significance of these dates from the wells of Chassidic wisdom. By Cha - http://www.chabad.org/holidays/3weeks/
Tisha BeAv - Essays on the role of Jerusalem in Jewish life, the holiday from an educator's perspective, and an online quiz. From the Jewish Agency's education department. - http://www.jafi.org.il/education/FESTIVLS/av/index.html
Tisha B'av Basics - Simple overview of the history and observances. Features list of dates for upcoming years. - http://www.jewfaq.org/holidayd.htm
Tisha Bav and Three Weeks in Sound - RealAudio classes about Tisha Bav and the three weeks leading up to it, including chanted versions of the Book of Lamentations (Eichah). From 613.org, a Hasidic audio website. - http://www.613.org/3weeks.html
Tisha B'Av and the Three Weeks - Halakha and Jewish thoughts on the meaning and observances of this period of mourning. From the Orthodox Union. - http://www.vbm-torah.org/3weeks.htm
Tisha B'Av - The saddest day on the Jewish calendar. Collection of text and RealAudio material to help your observance and understanding of the day and the City it stands to mourn. From the Orthodox Union. - http://www.ou.org/yerushalayim/tishabav/