Tu B'shevat rituals from Ritualwell.org.
T'ruah's Tu B'Shevat resource page, including a hagadda.
Judaism 101's Tu B'Shevat page
The Tu B'Shevat index page from My Jewish Learning: the Personal Gateway to Jewish Exploration. Includes links to several Tu B'Shevat haggadot as well as other activities and source material, sorted by level of Jewish background.
An article on Tu B'Shvat and vegetarianism by Richard H. Schwartz.
Children's site; stories about Honi Ha'Meagel
Torah Tots: coloring pages, word searches, codes
Trees, Earth and Torah: A Tu B'Shvat Anthology
Edited by Ari Elon, Naomi Hyman, Arthur Waskow.
“This anthology draws upon biblical, rabbinical, medieval, and modern sources--from art, music, recipes, and crafts, as well as fiction, poetry, and essays--about the significance and historical development of Tu B'Shvat, the Jewish 'New Year of the Trees,' and includes mystical writings along with Zionist and Eco-Judaism pieces. The anthology also includes several examples of preparing a 'Seder Tu B'Shvat.'”