I started using Skrill Moneybookers because it's used internationally. I can't use Amazon or Google Wallet because I'm in Canada and its taking them bloody well forever to get here.
Oh, and I just signed up for Zoompass.
I don't know how well it would work for commercial things, but for personal payments between people you know, Venmo is awesome. https://venmo.com/ (Still U.S. only though.)