I got this information from the US embassy in Oslo. As of today (Jan. 12) there are new visa rules for Norwegians wanting to travel to the US. Basically, instead of having to shove what's left of your last meal aside on your tiny little airplane table to fill out the green immigration form, you fill it out in advance via the web. If you already have a visa, you can use the ESTA-page to check its status.
United States Visa Waiver Program - ESTA Internet-Based Authorization Required for Norwegians Beginning January 12
Beginning January 12th, 2009, all Norwegian citizens must obtain approval through the Electronic System for Travel Authorization (ESTA) prior to traveling to the United States without a visa under the Visa Waiver Program (VWP).
ESTA is a Web-based system, available at https://esta.cbp.dhs.gov/ in 16 languages, including Norwegian. Under ESTA applicants answer the same few questions that have long been answered on the small green paper form I-94W (typically on the airplane prior to arrival). Eventually, ESTA will replace the paper form.
In most cases, ESTA will provide an almost immediate determination of eligibility for VWP travel. In a few case, however, determination may take up to 72 hours, so travelers are encouraged to apply well ahead of time. Applicants whose ESTA applications are denied will have to seek a visa in order to travel to the United States.
Travelers who have not received an approved travel authorization via ESTA may be denied boarding, experience delayed processing, or be denied admission at a U.S. port of entry.
Each approved ESTA application will be valid for a period of two years, or until the traveler's passport expiration date, whichever comes first. An approved ESTA allows for multiple visits to the United States within that period without having to apply for another ESTA. Specific U.S. travel plans are not required for ESTA application, so VWP travelers should apply on the ESTA web site as soon as they begin to plan a trip.
The ESTA requirement will apply to citizens of all 34 VWP countries. It is key to transforming the VWP from a program that evaluates security threats on a country-by-country basis to one that is capable of making traveler-by-traveler judgments. In addition to enhancing security, ESTA will provide for greater efficiencies in the screening of international travelers by reducing traveler delays at the ports of entry.
ESTA does not pertain to those who travel to the US with a visa. Individuals traveling on valid visas will not be required to apply for an ESTA.
The ESTA application is available here: https://esta.cbp.dhs.gov/esta
Read more about ESTA here:
More information about visas and travel to the US can be found here:
 ESTA(tm) is available now, and will be required beginning January 12, 2009, for VWP countries Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxembourg, Monaco, The Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland, and the United Kingdom. ESTA(tm) has been required since November 17, 2008 for new VWP countries: Czech Republic, Estonia, Hungary, Republic of Korea, Latvia, Lithuania, and Slovakia.
Kjapp forklaring på norsk
Internasjonale reisende som søker om å reise til USA under visumfritaks programmer, blir nå utsatt for strengere sikkerhetskrav. Alle kvalifiserte reisende som ønsker å reise under visumfritaksprogrammet må søke om reisetillatelse gjennom følgende prosess:
…dvs. ved å fylle ut skjemaet på ovenstående side. Da slipper du å fylle ut det grønne innreiseskjemaet man typisk får utlevert på flyet rett før landing. Det elektroniske skjemaet er på norsk, men må besvares på engelsk. Det er to deler: En for elektronisk søknad om innreise uten visum (tar deg til ny side), og en for å sjekke status på elektronisk søknad om innreise. Har du allerede gyldig visum, trenger du ikke å bry deg med ESTA-siden.