Mobile phone coverage is universal in urban areas and generally also good in rural Norway, though on occasion some rural valley areas might be badly covered.
Even in the most remote mountain cabins, as long as they are staffed, you will usually be able to send a postcard.
Most Norwegian households are connected to the Internet in some way (often broadband), making cybercafés hard to find outside major cities, due to a relatively small market. Most public libraries have free public access to the internet, but a limited number of computers and limited opening hours.
If you bring a laptop with a wireless connection you will find wireless internet zones just about everywhere (gas stations, city centres, cafés, shopping centres, hotels etc.). Be prepared to pay for it though. It is not unusual for hotels to have a terminal for guest use. Around 60% of camp grounds have Wi-Fi Internet, but if it's crucial for you, best to ask before paying for your camping space.
Telenor (national telecoms provider) sells pre-paid SIM cards for NOK49, providing fast 4G internet access capped at NOK10 per day. Speed is reduced after 500MB in a month, unless you purchase a further data package (another NOK49 / 500MB.Telenor stores (including the one at the airport) ask NOK199 for this SIM card, however you can purchase it in convenience stores for NOK49. Activation on-line requires a Norweigan ID, however Telenor stores can do this instantly for free for foreigners on presentation of your passport. (Prices as at May 2014)
As of August 2011, Telenor (national telecoms provider) sells prepaid wireless 3G internet dongles for computers (NOK700, about €100), NOK150 buy-in must be purchased with the dongle itself, that comes with NOK50 credit and 300MB of data to be used in 4 days. Then, another NOK150 purchase must be made for 15 days unlimited internet access. 3G speeds are very usable, and if 3G service is not available the dongle steps down to 2G (not so much fun). Of course, these prices and conditions may change quickly. There is a mobile phone shop at Oslo airport (landside) that sells phone equipment.
There are other providers; NetCom (part of the TeliaSonera group) offers coverage that is slightly less than Telenor but prices are better; NOK150 gets you a data-only SIM with 1GB data at 4G speeds for a week, NOK29 gets you 500MB for a day, or NOK200 for 2GB/2 weeks or NOK300 for 4GB/month. With voice the packages are 1GB+talk/text for NOK199, 3GB+talk/text for NOK299, and 6GB+talk/text for NOK399.