I too would recommend to look into André's book very much, and several articles by Deligne, esp. "Hodge I", "Valeurs de fonctions de L et Périods Integrales", "A quoi servent les motifs?". I found Nekovar's slides and Barbieri-Viale's "Pamphlet" usefull too.
Edit: Goncalo Tabuada held a talk on "the construction of the categories of noncommutative motives (pure and mixed) in the spirit of Drinfeld Kontsevich's noncommutative algebraic geometry program. In the process, I will present the first conceptual characterization of Quillen's higher K-theory since Quillen's foundational work in the 70's" (link). It would be interesting to know where one could read more about that.