Several online payment services are suitable for small businesses. Some popular options include:

1. **PayPal:** PayPal is widely used and offers a range of payment solutions, including PayPal Checkout for online stores and invoicing for service-based businesses.

2. **Square:** Square provides easy-to-use payment processing solutions, both online and in-person, with features like point-of-sale systems and e-commerce integrations.

3. **Stripe:** Stripe is known for its developer-friendly approach and is great for businesses that need a customized payment solution. It offers APIs for integrating payments into websites and apps.

4. **Shopify Payments:** If you run an online store, Shopify Payments is a convenient choice. It’s tightly integrated with the Shopify e-commerce platform.

5. **Authorize.Net:** Authorize.Net is a reliable payment gateway service that can be integrated with various e-commerce platforms and websites.

6. **QuickBooks Payments:** If you use QuickBooks for accounting, QuickBooks Payments can simplify the payment process by integrating seamlessly with your financial records.

7. **Braintree:** Owned by PayPal, Braintree is known for its developer-friendly tools and international payment processing capabilities.

8. **Square for Retail:** Square offers a specialized solution for retail businesses, providing inventory management and more in addition to payment processing.

The best choice for your small business depends on your specific needs, such as the type of business you run, your transaction volume, and your budget. Consider factors like transaction fees, ease of use, integration options, and security when making your decision.