Skyss is responsible for local bus routes from Bergen, Voss and Hardanger. Some bus routes run all year round, while others are only running during summer season. See Skyss's homepages for timetables and booking.
NOR-WAY offers express bus connections between Hardanger, Oslo, Sandefjord, Larvik, Kristiansand, Stavanger and Haugesund. See here for timetables and booking.