Unfortunately the reports I read don’t break down how the funds came through except to distinguish between individual and corporate donations. However, there is some data about candidate’s focus on raising money through display advertising.
Since January 2007, presidential candidates launched 277 million display ad impressions. And like in the primaries, Obama has taken the lead here. According to research by Nielsen Online AdRelevance, Barack Obama ran over 70 million display ads in January. Contrast that with John McCain’s 19 million display ad views.
Most of the ads are run on Yahoo, who is the leader for display advertising (Google tops search advertising). Recent numbers say that display ads make up about 21% of all online advertising.
I noticed that Obama, Clinton, and McCain all have very targeted sites with splash pages and home pages asking for contributions. Incidentally all three also have blogs.