Catholic Encyclopedia: St. Walburga: Fairly lengthy biographical article on this abbess of a double monastery, and author, who died in 777. Also known as St. Walpurgis or Waltpurde.
Catholic Online: St. Walburga: Paragraph-length biography.
For All the Saints: Walburga: Also called St. Bugga. Illustrated hagiography.
Patron Saints Index: Walburga: Illustrated profile, with links.
Walburga, Saint: Brief entry in the Columbia Encyclopedia.