The only land border is with Papua Irian Jaya, Indonesia, and crossing it involves some preparations but is not that difficult as it might have been. In Jayapura, Indonesia, there is a consulate to apply for a tourist visa. The consulate is located in Mendi, a 10 min green PMV public motor vehicle ride away from Jayapura's capital. The price is 2000 rupiah.
Depending on your Indonesian visa there are different options to cross the border. If you have a visa on arrival, issued to you for example at the Jakarta Airport, you can only cross the border using a boat or by stamping out at customs in Jayapura and then immediately traveling to the border 30km away. Western travelers attempting the latter should expect to pay some miscellaneous fees and jump moderate bureaucratic hoops before leaving.
Boats can be rented from Hamedi. Any other type of visa you can rent a car, or an ojek and cross the land border. If renting a vehicle for the crossing one should expect to pay approximately 300,000 rupiah from Jayapura town and travelers should expect to pay upwards of 500,000 rupiah to return from the border to Jayapura.
The ports include Madang, Lae, and Port Moresby on the mainland, Kieta on Bougainville, and Rabaul and Kimbe on New Britain. However, they are only internal ferries. International ferries are unavailable.