A wide variety of documents are already available, including census records, parish records, probate records, court records, and emigrant lists. These documents provide information about people's lives, in some cases going back to the 9th century.
Norway had mass emigration 100 to 120 years ago when roughly one-third of the population left the country. Many went to the United States with smaller numbers of emigrants to Canada, Australia, and elsewhere. The folks at the National Archives of Norway are aware that many English speaking descendants of Norwegian emigrants would like to research their heritage. As a result, the web site is available in both Norwegian and in English although the documents obviously will always be written in Norwegian. For those who never learned the language of their ancestors, a Norwegian-English dictionary can be a big help.
The Digital Archives of the National Archives of Norway can be found at http://arkivverket.no/eng. The starting page for parish records is at http://www.arkivverket.no/eng/content/view/full/629 and an example of a scanned register book may be found at: http://www.arkivverket.no/URN:kb_read?idx_kildeid=571&uid=ny&idx_side=-471. (Click on Control-Plus in a Windows computer or Command-Plus in a Macintosh to zoom in on an image.)
You also might want to check out the National Archives of Norway blog at http://dokumenteneforteller.tumblr.com/ that presents documents and photos related to a different theme every month. However, that blog is written in Norwegian.