We consider the resource allocation problem in cellular networks which support Device-to-Device Communications (D2D). For systems that enable D2D via only orthogonal resource sharing, we propose and analyze two resource allocation policies that guarantee access fairness among all users, while taking advantage of multi-user diversity and local D2D communications, to provide marked improvements over existing cellular-only policies. The first policy, the Cellular Fairness Scheduling (CFS) Policy, provides the simplest D2D extension to existing cellular systems, while the second policy, the D2D Fairness Scheduling (DFS) Policy, harnesses maximal performance from D2D-enabled systems under the orthogonal sharing setting. For even higher spectral efficiency, cellular systems with D2D can schedule the same frequency resource for more than one D2D pairs. Under this non-orthogonal sharing environment, we propose a novel group scheduling policy, the Group Fairness Scheduling (GFS) Policy, that exploits both spatial frequency reuse and multiuser diversity in order to deliver dramatic improvements to system performance with perfect fairness among the users, regardless of whether they are cellular or D2D users.