An old friend noticed a handy PDF called The Purdue OWL: Citation Chart, which gives sample citations for all sorts of things in MLA, APA, and Chicago style. And right on page 5, for “Article in an online magazine/ newspaper,” we have:
Bernstein, Mark. “Ten Tips on Writing The Living Web.” A List Apart: For People Who Make Websites. A List Apart Mag., 16 Aug. 2002. Web 4 May 2009.