Uber cart external payment system Now I working on project who need support some external payment systems (not PayPall or Google Chackout). I try search some tutorial/documentation about creation Ubercart payment system, but nothing found. So which way to look or where to start to solve this problem?
Basically, you need to create a custom module and let ubercart know about your gateway using hook_uc_payment_gateway(), then use hook_uc_payment_method() to define a payment method. 
Then, you continue with defining a form that is used on checkout and finish it with creating redirect to your external payment system.

You can start with this - http://nmc-codes.blogspot.sk/2012/07/how-to-create-custom-ubercart-payment.html, it should give you a good start.