I have been doing some work lately on how one can take payments or pay the client in the easiest way possible. This leads me to doing some research on currently available gateways. Some of the contenders are:
Paypal - a decent service, but takes a lot of money for transferring money. Its ok ..
Google Checkout - I am gonna checkout what it has to offer, should have a great API like all the other google products.
CCAvenue - it supports my debit cards so i really like them. They can become the yodlee of the indian web companies (if they can get some kind of an API act together)
Amazon payment gateway - beta beta … need an invite to use it … flat payment looks good
More as i keep adding to this research :).