Bonacich (1972) suggests that the eigenvector of the largest eigenvalue of an adjacency matrix could make a good network centrality measure. He defines Eigenvector Centrality as:
For more information about this formula, see:
Bonacich, P. Factoring and Weighting Approaches to Status Scores and Clique Identification. Journal of Mathematical Sociology 2 (1972), 113-120.