Good question, I’ve had questions about how to cite Internet resources on American Soccer News and also on this blog.
Matt Cutts does mention his own personal preference for linking at the top of the post, but that doesn’t necessarily mean anything as far as Google is concerned. You need to cite resources effectively for your readers and for other authors.
Why not link when you mention it? Unless you are going to be in-depth enough to make endnotes, write a bibliography or a works cited section, just link it when you mention the article or post.