The fees they charge vary, with some asking for more commission on each donation, others charging charities to have a presence on the site. But they all give charities the opportunity of a fundraising web presence they might not otherwise have had.
But some in the sector are concerned about the way in which they operate and fear there is a lack of regulation.
Catherine Clark, head of communications, marketing and development at the Royal School of Church Music, informed Third Sector she was unhappy that her charity was listed on aliveandgiving.com.
Charities are not consulted before information about them is put on the site - a major difference from other sites.
Clark said she found it "loathsome" that aliveandgiving.com was using the RSCM name to give its own business credibility. "However well-meaning the founders may be, they did not seek nor receive permission to make money from our donors at this or any rate of return," she said.
Chester Sinclare, founder of aliveandgiving.com, said charities were under no obligation to appear on the site.
"If they want their details removed, they can contact us," he said. Clark did this and the RSCM has since been removed.
So are there any guidelines governing this type of fundraising activity?
A spokeswoman for the Charity Commission said these sites did not need to be approved by it before being set up, nor did they need approval to use Charity Commission data on the site.
Sarah Tirrell, policy and codes of practice manager at the Institute of Fundraising, said that when people who wanted to set up fundraising sites contacted the institute, they were directed to relevant codes of practice.
These cover transparency and accountability in fundraising, and guidance for charities fundraising through electronic media.
James Sinclair Taylor, head of the charity team at law firm Russell-Cooke, said it was easy for someone to set up one of these sites.
"The Charities Act 2006 caters well for situations in which charities approach businesses," he said. "But not for situations in which someone chooses to fundraise for a charity without consulting it first."
Sinclair Taylor said charities often received cheques out of the blue after someone had raised funds without their knowledge. "The difference here is that a commercial body is making a living out if it," he said.