Some number crunching from The New York Times regarding the first wave of Rand Paul online fundraising:
After starting his campaign on April 7 with a "Stand With Rand" online appeal, his campaign brought in its first $1 million in less than 30 hours, from more than 15,500 donations….. The initial flurry for Rand Paul faded quickly. It took an additional 16 days for the figure to double.
….a disproportionate number [of Rand donors] have come from donors in smaller cities and towns. More than a quarter of Rand Paul's online donors list addresses in communities with populations of less than 10,000….
Only 4.7 percent of Rand's April online money came from people from cities with more than a million population, the Times analysis says.
He's drawing a lot, though by no means a majority, of donors from Ron Paul's fan base:
At least 2,000 of the donors to Rand Paul in April gave money to his father's 2012 campaign, an analysis of Federal Election Commission data shows; the number is very likely higher because many small-dollar contributors do not appear on F.E.C. filings.
The Times also mentions how Rand's father Ron really blew the roof off the sucker back in 2007 with what his fans organized and dubbed "moneybombs" seeking one-day fundraising records—and achieving them, with a then-record one-day haul of $6 million on Tea Party day, December 16, 2007. (Yes, the first big modern-era small-government "Tea Party" event was for Ron Paul, students of recent political history.) For some reason, the Times story mentions only an earlier, smaller $4 million day in November 2007.
Those big days for Ron were much later in the campaign process than April 2007 would have been, so I don't see a lot of percentage in comparing that moneybomb with Rand's take so far. The biggest Paul moneybombs were very much a grassroots fan process, not something led or managed by the campaign itself. Rand has many months to see if he can gin up a comparable amount of giving from an excited grassroots. He's certainly already way ahead of Ron in 2007/08 in the polls.
The story of Ron Paul's fundraising record, and much more, is told in my 2012 book Ron Paul's Revolution: The Man and the Movement He Inspired.