s2Member®—a powerful (free) membership plugin for WordPress®. Protect members only content with roles/capabilities.
Simple shopping cart system provides buy now buttons to purchase items via Paypal. Also links to Google Analytics to tracks sales.
Nice Google Checkout Lite gives you the power to create Google Checkout Buy Now buttons wherever you choose, by simply adding shortcodes to your posts
Adds Google Wallet as a payment gateway to the ClassiPress application theme.