Simple shopping cart system provides buy now buttons to purchase items via Paypal. Also links to Google Analytics to tracks sales.
Add "Add to Cart" buttons to your pages / posts with sidebar widget showing items currently in customer's shopping cart. When customer clicks on 'Go to Checkout' then can purchase items via Paypal. Simple, secure shopping cart system stores no user information (email, address, credit card, etc) but uses encrypted buy now buttons to pass customer over to Paypal for providing purchasing information.