The following short lecture series by Shaykh Taha Karaan methodologically covers the historical development of the Shafi’i school of Islamic Law (Madhab): http://www.shafiifiqh.com/audio-video/audio/[See update below]. This includes the Usuli development in the school, major figures that propagated the madhab, evolution of the madhab in different geographical locations including the impact they had on the outlook of the school, and the personalities that undertook the task of synthesizing or refining the variant opinions within the madhab.

This is an excellent resource for anyone wishing to gain deeper appreciation for the  intricate details and the complex machinery that went into the development of the Shafi’i madhab and by extension similar efforts in 3 other existing Sunni Schools of Law (Hanafi, Maliki, and Hanbali).