How can I get someone to checkout as soon as they add a product to cart?

This functionality is included on the product page and can be enabled in:

WooCommerce => Settings => Catalog => Catalog Options => Redirect to cart after adding a product to the cart (on single product pages)

But to accomplish this on the category page would more than likely require modifying the filter/hook within WooCommerce. Or customizing the content-product_cat.php file and it’s related files.

Take a look at http://wcdocs.woothemes.com/codex/template-structure/ for the guide to customizing the theme/pages.