As a generalization of cyclic codes, quasi-cyclic (QC) codes contain many good linear codes. But quasi-cyclic codes studied so far are mainly limited to one generator (1-generator) QC codes. In this paper, 2-generator QC codes are studied, and many good 2-generator QC codes are constructed using simplex codes. A computer algorithm is given, and used to find the best possible 2-generator QC codes. Among those 2-generator QC codes constructed, some codes are two-weight codes.