Thanks for the responses! Will, it sounds like you're envisioning a theme framework of sorts, which is what I was using with WordPress and Thematic before making the move to Silverstripe. I think it'd be a great idea to explore further with Silverstripe...
I'm not much of a back-end developer, so I figure this is the best way I can give back to the SS community. My idea is to create a nice bare-bones, modular grid-based structure that comes bundled with a handful of different skins. Once there's a solid framework underneath, extending that in different ways becomes a breeze. I'm also contemplating including some light JS scripts to provide basic functionality like animated scrolling (back to top buttons), tooltips, etc.
The more ideas I can get from the community the better, and if anyone would like to volunteer to review in-progress work just let me know :)