The Mamanuca and Yasawa Islands are easy to get to and numerous companies offer single and multi day trips. I will warn that accomodation in Fiji can be in the multiple hundreds to thousands per night, especially on small islands, or $30 for a clean bed and simple bathroom. There isn't much in the middle. With some advance planning Fiji is a fantastic vacation spot and as always be sure to get out of the resorts. Book a homestay, meet the locals, try the kava. You won't be sorry.
The Fijian islands consist of two large islands and over 300 smaller surrounding islands. Fiji conjures up images of white sandy beaches, low hanging palms, surf breaks, and crystal clear waters. While this is true, there are equally as numerous mangrove lined coasts, rocky shores, and beaches that are nowhere near as white as our home beach of Folly. Flying into Nadi on the large island of Viti Levu provides a good jumping off point to the outlying islands.
1. Viti Levu
3. Mana Island