What is the significance of dance in Praisesong for the Widow?
I agree with rayskx's comments, but I would also like to add that it is so important for Avey to start dancing again because she stopped dancing when she and her husband (early on in their marriage) decided that their dancing might reflect badly upon them. She and Jay bought into the idea that all African-American styles of dance were somehow uncouth, and, as they were trying to climb the social ladder in a predominantly white society, they did not want to be associated with it. Once Avey realizes finally that she has been self-loathing about her own race, she learns to enjoy dancing again. She appreciates her own African American heritage and the wider African Diaspora through her decision to dance again.
Dance is an essential part of Avey's African heritage. Remember that Avey's great-aunt Cuney did not perform the Ring Shout dance properly. The Ring Shout hails from a West African dance pattern, but Aunt Cuney was in a Christian church. Marshall is showing how the West African tradition was "translated" as it moved across to the Americas and changed through the years.
Avey finds the Ring Shout insignificant as a child, and her lack of knowledge of her heritage is a journey she must make both physically and spiritually. At the Big Drum dance towards the end of the novel, Avey understands the different dances of the different tribes that have been preserved, and dances her own version of the Carriacou Tramp. Lebert Joseph says that she is an "Arada." She will now teach others about their heritage in South Carolina.