Non for profit organisation Network for Good, a US based online donations company has raised $1.2B in online donations since 2001. They are backed by AOL, Cisco and Yahoo and in 2013 their online donations increased by 20% to $190M. Interestingly, they seem like the forerunner in the US online donations market, target only small to medium sized charities and ultimately account for well less than .1 of a percent of the $240B individual giving market in the US...
"Network for Good, a nonprofit that helps small and medium-size organizations raise money online, processed $190-million in online donations in 2013, up 20 percent over the previous year."