MONEY
The Currency of Papua New Guinea is the Kina.
This currency was originally based on the early form of shell money used, in which the Kina & Toea shells were traded for goods or used in special ceremonies and in brideprice payments. The name Kina, is the Tolai word for the shell, Pinctada maxima (White-lip Oyster),Toea is a word from the Motu language and also a type of shell.
There is 100 Toea in 1 Kina, and in 1975 when the Kina was introduced, it was on par with the Australian dollar.



Coin pieces originally came in 1,2,5,10,20 toea pieces, but today includes; 5,10, 20, 50, & 1Kina piece.

Notes are made of polymer (since 1991) and occur in denominations of; 2, 5, 10, 20, 50, 100
The Kina is highly volatile on the market and can range from 1/2 of the Australian Dollar to on par or even above it, which makes it very difficult to plan or run trips in the country. It's best to check the daily current rate and wait for a drop in the value before purchasing/ordering a quantity.
When travelling to the country, the best practise is to have a small amount of money to purchase your visa with and pay for a days eatings, but visit a local bank teller in Port Moresby, to get the best exchange rate possible.
Costs:
Papua New Guinea is rated as one of the worlds most expensive countries to travel in, however it is also rated as third-world status. There are two reasons for this; Firstly roads are almost impossible and dangerous to travel on, so goods, people and fuel is either shipped or flown around the country, which is extremely expensive but often the only means of transport.
Secondly, there are huge international mineral, timber, gas & oil interests. PNG is very rich in natural resources, though the money rarely reaches the hands of its population, except for the wealthy few. So shop prices are raised to whatever level the shop owners will think the 'mining community' can bare, often there are 'local prices' for those without industry wages.
That aside, local fish and veggies are much cheaper to purchase at the local markets, than in the first world nations. Prices for groceries in supermarkets are approximately double what one would pay, in say, Australia.
Unfortunately this can sway travellers away from PNG, however once you are outside of the big city centres, you will find the people very reasonable, friendly and accomodating. Almost 85-90% of the population in PNG are subsistence farmers, so they don't rely on a job to feed their families. Everyone in the family contributes to making a working community garden plot, with every family tending their own section. At market day (usually Fridays) everyone brings the extra pickings from their section of the plot to barter with other family plot pickings. This varies the diet of vegetable and meats and shares between families what one family could never grow on their own.
If you are visiting really remote areas and staying in small villages, the best thing to bring instead of money (as money is often not as useful) is small bags of sugar, rice, tea, coffee, milo, powdered milk, tinned fish, etc. as these are great for bartering for a nights' home stay or fresh fruit you may like to have while in the area.... Clothing, medical supplies and books are also useful and something they can use again and again.
Links to Current Kina Information:
Bank of PNG
Other interesting links
Pacific MonetaryTradition