Best way to accept donations online - Can't use paypal

Hi, I'm making a site for a non-profit and I need to be able to handle donations online. I can't use paypal because the donations need to be seamlessly integrated with the site, also I will need to do a fair amount of customization to the donation forms, like matching funds, gift in another person's name, and allocating funds for specific purpose. Does anyone have any good recommendations? thanks, Dave