I like Piryx because it’s easy to set up and configure. It has lots of social sharing options and you can create multiple online fundraising campaigns. You can theme pages to look like your site, add your logo, etc.
As for the fees, from their site:
There are no monthly fees, no startup fees, no contracts, and no initial costs. The only costs associated with using Piryx is a 4.5% transaction fee on money that you raise through Piryx Fundraising, which includes merchant, credit card (Visa, MC, AMEX, Discover) and eCheck processing fees.
They have a tiered pricing model as well:
$0 – $100,000 – 4.5% per transaction
$100,001 – $250,000 – 4.3% per transaction
$250,001 – $1 Million – 4.25% per transaction
$1 Million+ – 4.0 % per transaction
They accept major credit cards and eCheck.
With Piryx, they take care of pretty much everything, it’s easy and intuitive. There’s one central location which is nice too – rather than setting up multiple forms across places like your Website, Twitter, Facebook, etc. They also handle all the mobile development so the donation page(s) work on iOS and Android platforms as well.
Perhaps best of all, they’ve done tons of research and have gobs of stats to work with, so they can optimize the donation forms & pages to get the best conversion rates. That’s pretty much all they do, so they’ve gotten pretty good at it.
They have more info on their FAQ page as well as videos there.
It’s really pretty awesome and you can get going quickly. They also have a recent update that has been spun off into Rally. I haven’t really dug into this yet but it looks slick as well!