Depends what you are interested in, but a trip on the Sepik River takes you to numerous villages where the people engage in subsistence farming and fishing, as well as those that engage in handicrafts (mainly wood carvings). We were on the (if I remember the name correctly) MTS Discoverer out of Madang.

The diving in PNG is very good. Although there are many areas in which to dive, our diving was out of Kimbe Bay.

Many expats in Jakarta rave about adventure travel with Leks Santosa
http://www.expat.or.id/sponsors/remotedestinations.html

This would be West Papua, but same island, same fascinating culture. Leks is an Asmat specialist and, from what I'm told, his tours are well organized and unforgetable. Many people I know have gone back again and again.

Thanks Susncrg and Marmot for your replies. I will check these companies out. Diving, culture and some hiking would be nice. I am not sure exactly what we want to do there, but seeing the "sing-sing" festivities and culture are at the top of the list.

Ingrid

Alas, the MTS travel agency and their great boat MS Discoverer are no more - the boat was sold in November.

If you do a search for P.N.G. tours all you seem to get is TransNiugini tours who steer you through various vastly overpriced properties, then down the Sepik on their vastly overpriced boat - Personally I think they're a rip off but they will get you through.

Right now, with MTS just gone, there's only www.ngholidays.com [niugini holidays] left - but, try as I might, I can't raise their website any more.
Perhaps they've gone down as well.

There are tours - you'll find them with a cursory search [try 'niugini' instead of 'new guinea' - but they are very expensive, much more so than they should be.

Try and time your visit for one of the major sing-sings [festivals]

And, if you can get to the Trobriand Islands, you won't regret it.

It's the most extraordinary country - you'll come back blown out.