Or...if you know you should be more charitable......

I don't use my real credit cards online (had a bad experience around 2006 in which I was charged for services from a site I never visited; I never got my money back and was treated like a lying criminal... fuck you BMO! I switched banks and never again!) I'm also morally opposed to paypal so I use disposable "gift" credit cards for online purchases when needed. If my remaining balance is under $15.00 (because what can you buy for that?) but more than $5, I'll make a small one time donation (usually to a FOSS project or crowd funding campaign of some sort). I make sure it's more than $5 dollars though because I don't want to cost them in processing fees.

I work downtown so if I'm down to a balance under $5 I write the balance on the card in sharpie and "drop" it on the street for a homeless person to find. Some real life merchants do take anonymous disposable credit cards for small purchases, but I can't be bothered to bitch and complain at the counter for the price of a pop and pack of gum.