My instance defaults to the category page because I personally think that page is the ‘cleanest’ for new visitors. By clean, I mean less intimidating, less options and buttons everywhere and the purpose of the site is more immediately evident. I use Manual’s great Featured Topic component to place two topics on top of the category list. It uses a tag so two pre-chosen topics show. Some css magic makes the two topics appear with just the picture and a short intro. I use Don’s Close Sidebar by Default component to always present the landing page without the left hand side menu closed.