Visa, Wells Fargo Deliver SET Alternatives
New options for handling credit card transactions over the Web are emerging as cheaper and simpler alternatives to the dormant SET standard.

Visa - Electronic Commerce - SET
Secure Electronic Transaction (SET) information, including links to press releases, specification files and reference implementation.

Making Sense of Specifications: the Formalization of SET
Extended Abstract by Giampaolo Bella, Fabio Massacci, Lawrence C. Paulson, and Piero Tramontano.