The Humanity Quest website promotes the exploration of 500 values, including humility. A search under any particular value will give you links to resources that may include quotations, art and other activities, e-lists and newsletters dealing with this value, art that expresses this value, and reference material.
Read an interesting, scholarly article on boasting: "Flytes of Fancy: Boasting and Boasters from Beowulf to Gangsta Rap" by Alta Cools Halama in Essays in Medieval Studies.
Mother Nature has a way of humbling us all, especially when a natural disaster occurs. In his article "Humility in a Climate Age," Paul Wapner (Tikkun magazine, May/June 2010) looks at two ways to approach our current environmental crisis: with humility, which calls for lifestyle changes, or with "mastery," which argues that we should devise technologies to fix our problem.