Ask HN: best ways to charge people online for small, punctual purchases?

Kind of like "in-app purchases" in iOS. Not recurring and in the $1-2 range. Facebook credits? Paypal? Selling a bigger package of credits in the $10-20 range to be used over time (similar to Skype for example)? Regular payment systems would work of course but they tend to have a lot of friction and include multiple steps, where two clicks would be nice. And, though I'm not familiar with the exact prices, I'm not sure the commissions are interesting for multiple $1-$2 purchases. How have you done it? Thanks!