Make sure to step outside the tourist areas - even if it's only for half a day - so that you'll get to see a side of Malaysia that's very different from that of the resorts.
Selingaan Island is the only island in Turtle Islands park which is open to the public. Green Turtles and Hawksbill Turtles visit the beaches year round to lay their eggs.
Sepilok Nature Resort & Orang Utan Sanctuary. Irrespective of the orangutans, Sepilok Nature Resort offers the chance to see the real rainforest before all of Sabah's rainforest is swallowed up by consumerism.
Quick Tips:
If you have the opportunity, do the 2-day trek up Mount Kinabalu. Unfortunately, I damaged my arm partway through the trip and so was unable to make it, but it's on my must- do list for next time.
As the tallest mountain in South East Asia, it offers unrivalled views of the countryside (on a clear day at least!)...and it's visible on the horizon even as far east as Selingan Island. With such a presence, it's no wonder Sabahians are so proud of their mountain.
Best Way To Get Around:
Unfortunately, even in the main cities, walking is not easy with pavements crumbling or being rebuilt and open manholes and sewers where there are paths.
Likewise, the main historical and cultural attractions seem to be located too far from the resorts for a comfortable walk. Best way to get to these is by taxi (teksi).
If you're more of a shopper than a historian, use the resort shuttle bus or the local buses to take you into the town/city centre and then walk from plaza to market to plaza.
The quickest route from one side of Sabah to the other is by air...however, I feel we missed out on a lot of 'real' Malaysia by not driving.