"Buy Now" takes you straight to the checkout to buy single items.
You can also have the shopping cart always visible on the page, which soort of removes the need for a cart review page between adding stuff and checking out.
Or how about a "Buy random stuff!" button that puts a few items in the cart at random and goes to the checkout.
Actually, "Buy $100 worth of this item" might work for bulk buy products. (and the $100 can be set to any amount of course).