The detail available in the extensive parish church records is a marvelous gift from Norway. The Digitalarkivet web site has been adding scanned images of the original Norwegian parish church records for anyone with Internet access since November 2005. To be able to use the parish records you must first know WHERE in Norway you want to search for this documentation.
The Digitalarkivet web site - (http://digitalarkivet.uib.no/cgi-win/WebFront.exe?slag=vis&a...
An English option is available by clicking on that word from either the left hand column or the blue link bar along the bottom of the homepage.
The scanned images are available from the homepage link "Skanna kyrkjebøker" [Norwegian version]/"Digitised parish records" [English version] which is listed along the left hand column and from the blue banner of links along the top section of the homepage.
When you click on that link another page will present a short list of choices - choose "Read the digitized parish registers"[English version]/"Lesa skanna kykrebøker" [Norwegian version].
After you've clicked on that link and a new main page has presented on the screen be sure and read the instructions that are available from the Digitalarkivet for navigating the scanned records. The instructions are available in Bokmål (official Norwegian), Nyorsk (Norwegian), Davvisámegiella (Saami), and English.
Recommended basic reading are the "Startsiden" [Norwegian version]/"Main page" [English version], "Brukerveiledning" [Norwegian version]/"User's guide" [English version] and "Om tjenesten" [Norwegian version]/"About this service" [English version].
Good information about translating the formats of Norwegian parish church records during various time periods, many of the basic terms used and understanding how to use the information should be studied at this web site -
Norway has a tradition of publishing history and genealogy books for many rural districts of the country called 'bygdebøker'. You might be lucky enough to have had ancestors from one of the areas which has one or more good 'bygdebøker' published about it.
Learn about 'bygdebøker' (http://homepages.rootsweb.ancestry.com/~norway/bygdebok.html
Bygdebøker and Ættarbøker can be helpful but are definitely secondary sources of information -- any research done in them should be verified in the primary sources such as the parish church records.
For Sauherad, Telemark there is the multi-volume "Bygedebok for Sauherad, gards og ættesoge" by Birger Kirkeby. The library catalog of the Family History Library in Salt Lake City shows that they have copied all or most of those books to microfiche that can be ordered and used at any of their many LDS Family History Centers around the world.
(Be sure and have a good Norwegian-English dictionary before trying to use a book written in Norwegian.)