Classifying Scandinavian tunes is a completely arbitrary activity. Most of these tunes are played for dances, and the same tune can be used for different dances. As a practical matter, many musicians group tunes together by dance type (especially for gammaldans, the more recent layer) and/or by region (especially for bygdedans, the older layer). This is the method I have used. (See here for a brief discussion of folk music basics.)
Most Scandinavian tunes do not have unique names that can be used to identify them. Any individual tune may be listed in more than one category, although I have attempted to list each tune only once (please contact me if you find an exception). If you can't find something you're looking for, try searching for its number (if you know it) or a relatively unique word from the title or the dance type. Failing that, you'll have to scan the incipits pages below.
A detailed explanation of the annotations for each tune is available here.
Warning -- I am in the process (2015) of converting from the old Blue Rose site of 2005 to a new, responsive, mobile-friendly version. This is going to take quite a while for the incipits pages. In the meantime, when you click on a tune category you will sometimes get a newly-formatted page (widgets, mobile friendly), and sometimes an old one (tables, not-mobile friendly). They look rather different, but they contain the same information either way.