What are some alternatives?
When comparing Affiliatly and Google Ad Manager, you can also consider the following products
Refersion - Seamless influencer tracking system for online retailers.
OpenX - Ad technology platform available as a hosted service or as an open source download.
ShareASale - ShareASale
AerServ - AerServ offers monetization solution for mobile publishers.
TrackingDesk - Conversion Tracking & Attribution platform for performance marketers.
ONE by AOL - Ad Serving and Supply Side Platform (SSP)