MyVirtualCard.com does adult, and if Stormpay is still around, they are a Paypal-like business that is OK with adult. I think Moneybookers.com also has a similar program and is adult-friendly.

Depending on what you're doing, Epoch and CCBill will work, but their model is much more set up for recurring membership-based payments. I'm not sure they'll allow a "donation-based" setup like you're speaking of.