I've tried a lot of different payment processing companies for various online businesses and I've compiled a list of only those that are easy to use from the buyer's perspective.

PayPal

PayPal is a great option for those just starting out and looking to keep costs down and website integration easy. PayPal has been around for ages and many small business owners use it every day.

The one issue that I have with PayPal is that it makes your customers feel forced to set up a PayPal account during the transaction process. This takes away from the buying experience and can send some potential customers running for the hills if they aren't familiar with PayPal.

Aside from that it's a great system for a small business with rates (at time of this post) of 2.9% plus 30 cents per transaction. You can easily create buttons and a shopping cart system for your website and even manually create great looking invoices to send to your clients for payment.

Square

Square is a fantastic option for small businesses that have a storefront or sell items at fairs and events. After signing up, you'll be sent a small card reader in the mail that connects to your phone or ipads headphone jack. Load the app, swipe your customer's card and that's it!

Your customer can sign with their finger right on your phone and you'll have the option to send them a receipt by email or text.

Truly an awesome solution for people who do business in person. They do not however have a system to integrate with your website for online payment so you may end up with two different payment providers if you need an on-site and in person payment solution.

That said however they do offer the ability to send online invoices meaning you can send your invoice by email directly from your phone app or using the online portal which they can pay by credit card.

You can use Square as your complete retail point of sale system. They have a very cool stand the holds your iPad and has an integrated card reader and USB hub to connect your cash register, receipt printer and bar-code scanner.

There you have it. Square is in my opinion the easiest payment system for small business owners who do in person commerce. At time of writing, square's rates are 2.65% per swiped transaction, 2.75% per square invoice and 3.5% plus 15 cents per transaction for manually entered transactions, not using the card reader. Pretty fair pricing compared to some of the other options.

Stripe

The Stripe payment system is a more advanced solution that offers developers and people with a bit more IT skills to integrate a payment solution directly into a website or app.

Although you may need to pay someone to set this up, the integration is a much more seamless process with your existing site or app. You customers will never know they are dealing with a third party payment processing system because they don't have to leave your site.

The payment interface simply pops up on the screen and they can enter payment information without being redirected to the payment processors website, like PayPal.

Pricing is a bit higher that other options at 2.9% plus 30 cents per transaction.

2Checkout

2checkout is a great PayPal alternative with really nice website integration including support for recurring subscription payments. Their payment system looks great on desktop and mobile devices.

They support shopping cart system as well with many customization options specific for your products, like color, style, men's, women's and other attributes. If you're looking for even tighter integration, 2checkout supports API integration for developers as well.

Pricing is a bit on the high side however at 2.9% plus 30 cents per transaction.