I have been using MachForm for a non-profit site that I am running.
I use it for the Donations page, Raffle page, and also the Nominations page (online form).
However, at the moment the Nomination Form is disabled as their Induction Ceremony is happening this weekend and they are not accepting nominations again until afterwards.
Payments can be made through PayPal, Stripe, Authorize.net, Braintree, or via mailed in check/cash.
It can be a bit more work than some others, but you have a lot of options available with it as far as setting everything up and designing the form.