Checkout/carting system (with PayPal)

Know the difference between;

Parallel Payments - Developers can enable buyers to send money to several people in one payment, which is ideal for purchasing multiple items from different sellers, or even for payroll applications.

Adaptive Accounts API - Provides a streamlined signup experience for people who don’t have PayPal accounts, while maintaining security and privacy of consumer data. With the new API, developers can create PayPal accounts for their customers from within their applications.

Paypal - Adaptive Accounts

1. Adaptive Accounts Scenarios: Marketplace
2. Why use Adaptive Payments API: Make split payments to multiple recipients
3. Send and Receive Payments Securely Worldwide

Rails + Paypal

1. Google search results
2. RailsCasts
3. PayPal Adaptive with Rails 3
4. ActiveMerchant + PayPal Adaptive

PayPal Adaptive Github Repos

1. Active Paypal Adaptive Payment
2. Tommy Chheng's PayPal Adaptive