Hi,
I think I read somewhere that someone mentioning Flattr. However, the amount that can be donated is pretty limited. Another thing I just got to know about Flattr is that they have an offline version called Flattirl. It generates a QR code that you can use at venues, etc., and people just have to flash your barcode to access the Flattr button and donate.
I dont know if it might help you in some way. Good luck.