When I think of the best program, the first one that comes to mind is always
PimpRoll. However, while they routinely roll out brand new sites, most of their exclusive content sites tend to stop adding new content not long after their initial launch, with the respective feeds continuing to recycle through previous updates.
Other than that, they offer great tools, on time payments (weekly/no minimum!), and are almost always prompt to reply to affiliates and/or take action on concerns brought to their attention.