December 12th and the preceding week is a marvelous time to witness one of Mexico's proudest and most important traditions, pilgrimages acrosss the country to honor Tonantzín, the Mother of the Earth, known more commonly nowadays as Nuestra Señora de Guadalupe, often mistakenly but lovingly referred to as "La Virgen" or "La Virgencita", from Catholicism's influence.
There is a bit of info in the Message Board Archives that you may find useful.
Nuestra Señora de Guadalupe
Nuestra Señora de Guadalupe (Tonantzin)
Himno Guadalupano
Danza de los Tlacololeros