There is a comprehensive bus network in Fiji, ranging from modern air-conditioned coaches to local buses with no windows - just canvas flaps in case of rain - at the other end of the spectrum. The local buses are particularly enjoyable as you get a chance to meet the locals and soak up the atmosphere.
Virtually everywhere on the main islands is connected by bus and it's not a problem if you can't find the bus stop - if you see a bus, just wave to the driver for it to stop.
In more remote regions, buses are replaced by carriers. Carriers are usually minibuses or pickup trucks converted into public transport. This form of transport is a little more uncomfortable and the fares may be a little higher than buses, however carriers are definitely a great way to experience Fiji.
The Feejee Experience is a backpackers' bus that runs a circuit around Viti Levu with overnight stops in Nadi, Coral Coast, Raki Raki and Suva.