We're using the nicepaypal button on some sites. Below I have copied the instructions on how to write the code to put intor your article.
Some tips:
If the buttons don't show on the site. Check the source to see if the code is included in paragraph tags <p></p>, if it is, deletet the paragraph tags while you're in source mode.
If you click the buttons and they go to the PayPal sandbox area. Check the configuration and where is says "test" replace the "true" with 0.
Below is a copy of the documentation page. The original can be found through this link http://www.trinitronic.com/index.php/Downloads/nice-paypal-button-documentation.html