Which payment provider, such as PayPal, should I use for marketplace style site?
Shopify is a good shopping cart site. They have a comprehensive list of payment processors, here, that can be used on any site, not just theirs. I think your question is very broad though and I don't know what your goal is. I think you should look into the providers below and which one fits you needs the best.
That being said, paypal is one of the best payment providers as far as rates go. I have heard that people have fraud issues with them sometimes.
- http://www.authorize.net/ - Authorize.net
- http://www.beanstream.com - Beanstream
- http://www.braintreepaymentsolutions.com - Braintree
- http://www.cardstream.com/ - CardStream
- http://www.cybersource.com/ - CyberSource
- http://www.datacash.com/ - DataCash
- http://www.e-xact.com/ - E-xact
- http://www.concordefsnet.com/ - Efsnet
- http://www.elavon.com/ - Elavon MyVirtualMerchant
- http://www.instapayllc.com - InstaPAY
- http://www.linkpoint.com/ - Linkpoint
- http://merchantwarehouse.com/merchantware - MerchantWARE by Merchant Warehouse
- http://www.modpay.com - Modern Payments
- http://www.moneris.com/ - Moneris
- https://www.nelixtransax.com/ - NELiX TransaX
- http://www.netbilling.com - NETbilling
- http://www.netregistry.com.au - NetRegistry
- http://www.ogone.com/ - Ogone DirectLink
- http://www.paymentsolutionsltd.com/ - PSL Payment Solutions
- http://www.payjunction.com/ - PayJunction
- https://www.paypal.com/cgi-bin/webscr?cmd=_payflow-pro-overview-outside - PayPal Payflow Pro
- https://www.paypal.com/cgi-bin/webscr?cmd=_wp-pro-overview-outside - PayPal Website Payments Pro (CA)
- https://www.paypal.com/uk/cgi-bin/webscr?cmd=_wp-pro-overview-outside - PayPal Website Payments Pro (UK)
- https://www.paypal.com/cgi-bin/webscr?cmd=_wp-pro-overview-outside - PayPal Website Payments Pro (US)
- http://www.commsecure.com.au/paysecure.shtml - PaySecure
- http://www.paymentexpress.com/ - PaymentExpress
- http://www.plugnpay.com/ - Plug'n Pay
- http://www.psigate.com/ - Psigate
- http://quickpay.dk/ - Quickpay
- http://www.realexpayments.com/ - Realex
- http://www.sagepayments.com - Sage Payment Solutions
- http://www.sagepay.com/ - SagePay
- http://www.securepay.com/ - SecurePay
- http://securepay.com.au/ - SecurePay (Australia)
- http://www.securepaytech.com/ - SecurePayTech
- http://www.skipjack.com/ - Skip Jack
- http://transfirst.com - TransFirst
- http://www.trustcommerce.com/ - Trust Commerce
- http://www.usaepay.com/ - USA ePay
- http://www.verifi.com/ - Verifi
- http://www.viaklix.com - ViaKLIX