There are a few things to do at Rainbow Beach, though at the end of the day it is just a small beach community.
The main beach area is well patrolled, and free from vehicle traffic. It is a wide flat, white/golden sand beach. From the beach you can see south to Double Island and north to Frazer Island.
If it is December - March, look up and you might see hang-gliders above the coloured sand cliffs.
The hang-gliders launch from Carlo Sand Blow, a great saddle of sand at the top of one of the dunes. It is worth visiting. It is, I guess, a large sand dune, about 500m * 500 metres, and can be reached via a pleasant and easy bush walk of about five minutes.
Throughout spring and summer there are usually a few people fishing along the beach. They usually catch a few.
There is very little nightlife to speak of (a pub, a surf club and a bowls club), but December and January is high season and there are usually a few bonfire parties on the beach.
From Rainbow Beach you can take day trips north to Frazer Island or south to Double Island point, or into the Cooloola National Park, which surrounds the town.