Here's a SQL Script to help you get started on importing from the Announcements module to Efficion's Articles module.

INSERT Article(PortalID, UserId, [CreatedDate],[Title],[Article],[Description],[PublishDate])
SELECT PortalID,CreatedByUser,[CreatedDate],[Title],'external:'+[URL] as Article, [Description], [PublishDate] FROM [Announcements]
ORDER BY PublishDate