Let's say I'm making a site similar to e-bay (connecting buyers and sellers). Which payment provider should I use as of today?
Which payment provider, such as PayPal, should I use for marketplace style site?
payments
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.nethttp://www.beanstream.com - Beanstreamhttp://www.braintreepaymentsolutions.com - Braintreehttp://www.cardstream.com/ - CardStreamhttp://www.cybersource.com/ - CyberSourcehttp://www.datacash.com/ - DataCashhttp://www.e-xact.com/ - E-xacthttp://www.concordefsnet.com/ - Efsnethttp://www.elavon.com/ - Elavon MyVirtualMerchanthttp://www.instapayllc.com - InstaPAYhttp://www.linkpoint.com/ - Linkpointhttp://merchantwarehouse.com/merchantware - MerchantWARE by Merchant Warehousehttp://www.modpay.com - Modern Paymentshttp://www.moneris.com/ - Monerishttps://www.nelixtransax.com/ - NELiX TransaXhttp://www.netbilling.com - NETbillinghttp://www.netregistry.com.au - NetRegistryhttp://www.ogone.com/ - Ogone DirectLinkhttp://www.paymentsolutionsltd.com/ - PSL Payment Solutionshttp://www.payjunction.com/ - PayJunctionhttps://www.paypal.com/cgi-bin/webscr?cmd=_payflow-pro-overview-outside - PayPal Payflow Prohttps://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 - PaySecurehttp://www.paymentexpress.com/ - PaymentExpresshttp://www.plugnpay.com/ - Plug'n Payhttp://www.psigate.com/ - Psigatehttp://quickpay.dk/ - Quickpayhttp://www.realexpayments.com/ - Realexhttp://www.sagepayments.com - Sage Payment Solutionshttp://www.sagepay.com/ - SagePayhttp://www.securepay.com/ - SecurePayhttp://securepay.com.au/ - SecurePay (Australia)http://www.securepaytech.com/ - SecurePayTechhttp://www.skipjack.com/ - Skip Jackhttp://transfirst.com - TransFirsthttp://www.trustcommerce.com/ - Trust Commercehttp://www.usaepay.com/ - USA ePayhttp://www.verifi.com/ - Verifihttp://www.viaklix.com - ViaKLIX