I've recently gotten hooked on buying tshirts from the internet. Especially ones that have to do with Dr. Who and other geeky subjects. TeeFury, a website that offers up a new tshirt design every day, has quickly become one of my favourites.
What I love about TeeFury is that they've streamlined the buying process so well that before you know it, it's being shipped to your door.
And I think that the most significant key to this is a simple button placement and some cheeky commentary that goes along with it.
The "unnecessarily large button" is a user's dream. A lot of sites clutter the checkout experience to the point that you never know exactly what you need to do to complete your transaction. Not so here, and it's appreciated.