The individual places have their own airlines, and generally cover one island over, so you can make an itinerary as long as you're patient and willing to search on the little airline websites - overall search engines don't seem to index these airlines. Also, many times the flights are once or twice a week, so try a lot of dates to see the pattern.

For example, start in Australia and take AirCalin to New Caledonia. From there AirCalin again to Vanuatu. Fiji Airways to Fiji, and then later to Samoa. Here you run into trouble and have to pop down to Auckland, from where you can carry on to the Cook Islands. Air Raratonga will take you from there to Tahiti, and LAN will (once a week) take you to Easter Island, from where they have daily flights to Chile.

With some sort of backbone in place you can then look for spikes out from individual islands, such as a day trip to American Samoa from Samoa, that sort of thing.