I'd use a lightly blinking notice box at the top of your screen, just below the header. Let it disappear when not clicked within 5 seconds or so. Give a teaser, with a link to take the tour around new features. Only do that when you have several that are worth the time to learn about. BTW - I'm from a marketing/sales background and just getting into IT/Comp.Sc. maybe we can learn from eachother? My email is in my profile.