Every day in English speaking countries, we see vestiges of the Norse religion. The days of the week correspond to Norse gods. So, Thursday is Thor's day and Friday Frejya's day. Wednesday is Odin's day and so on.
The term Yuletide references the Jul festival, but how much do we actually know of the religion and the religious practices?
It is very difficult to say. The main source of Norse religious belief are the Eddas--the poetic and prose Eddas that were written/collected in medieval Iceland. Snorri Struluson, the 13th century Icelandic chieftain is generally credited as being the author.
The main trouble with them is they were written down after the Viking age had ended and the religion had ceased to be practiced. So we know some of the myths, but not really the ritual. You could argue, I suppose, that December's St. Lucia Day with its candle-crowned maidens and star boys reflects how some of the ceremonies were carried out, but by in large, we don't know. Also given that other forms of literature had reached Iceland by that time, it is possible that they were contaminated, but the Eddas are the main reason why we know something about Norse religion.
Edda means literally "great-grandmother" and it is uncertain whether or not the Eddas were originally called that. The original codex have been long lost. They are collection intended to inform skalds on the tradition form of Icelandic or skaldic poetry. And were thus suppose to be the basis of all Icelandic poetry and literature tradition.
Because medieval Iceland was a highly literate society, great care was taken to preserve the Eddas by repeatedly copying them. The first English translation of the Eddas dates from 1770 and Bishop Percy. In 1809, Sir Walter Scott printed his own version with additions and the popularity of the Eddas in the 19th century world was firmly established.
When you go to Rejkjavik, it is possible to visit the Culture House and see the remaining manuscripts. The exhibit is very accessible with a wide of variety of the originals displayed. Included in the exhibit is an exhibit of work dedicated to those works that have been inspired from the Eddas and the other sagas. So for example, Tolkien's Middle Earth and Wagner's Ring Cycle as well as WH Auden, Longfellow, and Jorge Luis Borges are highlighted.
It is through the Eddas that we are first allowed a glimpse into the world populated with elves, dwarfs, giants and gods and our literature is far richer for it.