Awesome
LGLinearFlow
LGHorizontalLinearFlowLayout - iOS Collection View flow layout with zoom effect and variable page size
Objective-C: LGLinearFlowView/Classes/Core/LGHorizontalLinearFlowLayout{.h,.m}
Swift 2.0: LGLinearFlowViewSwift/Classes/LGHorizontalLinearFlowLayout.swift
Scale offset and minimum scale factor parameters can be used to fine tune the effect. Check out the sample app for more details regarding implementation.