as seen at lwn: "IBM has released the Universal Description, Discovery and Integration (UDDI) libraries as open source for Java developers. 'The Universal Description, Discovery and Integration initiative, launched last year, is a multivendor effort to create registries for Web services, allowing companies to automatically discover each other and do business over the Web.'"
Put simply, UDDI is a corporate registry framework, providing a standard API for white/yellow-pages services to enable ecommerce. In other words, this allows any business to specify which ecommerce functions they support, and it's all centered around corporate name authority control. For concrete examples of what code will look like, see this overview on the developerworks site.