The Digital Giving Index
The Digital Giving Index, produced annually by Network for Good, looks to charity websites, charity portals, and social giving (peer-to-peer) websites to analyze online giving trends. The 2014 Index Good examined the $233 million in online donations to 45,000 nonprofits that was processed entirely by Network for Good.
M+R Benchmark Study
The M+R 2015 Benchmark Study provides data regarding online fundraising, advocacy, and list building. This year, the M+R Benchmark Study analyzed the data of 84 nonprofits, producing a wide-ranging assortment of online nonprofit metrics.
The Blackbaud Index of Online Giving
Blackbaud's index covers the online giving trends of over 3,786 nonprofit organizations representing $2 billion in yearly online giving. The Index is based on actual revenue statistics from nonprofit organizations of all sizes and a variety of missions.
More reports, such as how online varies by the size of the charity and by the mission of the charity, can be found on the Blackbaud site here.