Ever read the study of atmospheric flight on Venus? It focuses more on sustained flight than gliding to a landing, but it's still the first thing I thought of.<p><a href="http://media.cleveland.com/science_impact/other/Landis%20Venus%20atmospheric%20flight%20study%202002.pdf" rel="nofollow">http://media.cleveland.com/science_impact/other/Landis%20Ven...</a>
I bet the core components would be reusable on other atmospheres. You could imagine spiraling down into Jupiter's red spot or the giant hexagon on Saturn.