It wolud be nice to have alternative payment gateways in addition to PayPal. As you can know, PayPal does not allow to accept payments in some countries (like Russian Federation). So, I've bought nice application a few months ago, discovered this fact and have never used it.
In Russian Federation we have a lot of alternative online payment services, such as WebMoney, Я.Деньги & others, аnd a lot of payment gateways to deal with all of them. In most cases all communication with this gateways works close to PayPal: we have payment url, success url, deny url, and s2s transaction request.
So, some kind of plugin system (base payment class and configurable extenders for it) with page in ACP to enable/disable and organize them will be enough to make Donation Tracker really universal system. I can provide plugins for all popular Russian payment gateways, so some other people will add their favorite systems and that'll be really good for all of us :)
