Nanna is the faithful wife of Balder, and the daughter we are told of Nep. Nep is not spoken of anywhere else in the Eddas or Sagas so we do not know if Nanna is of Aesir, Vanir, or Jotun stock. I believe that she is descended from Aesir stock. We do know that with her husband Balder she had one son named Forseti. It is only through the story of Balder's funeral than we gain some insight into the Goddess Nanna. The Eddas tell us that when a distraught Nanna saw Balder's body lying on the funeral ship her heart burst from sorrow and she died. The Gods took her body and laid it next to Balder ( and his horse ), and then set the ship on fire and with the help of a Giantess launched the ship on its journey to Hel.
We next hear of Nanna when she is Niflheimwith Balder. Hermod, taking up the challenge set forth by Frigga, rides Sleipnir to, and over, the Gates of Hel to bargain with the Mistress of Niflheim for Balder's release. While visiting with Balder, Nanna gives Hermod linen cloth for Frigga, and a finger ring for Fulla, to bring back to Asgard with him. The bargain was struck and Hel agreed to release Balder if everything in the nine worlds shed tears for Balder. When Hermod tells the Gods of this they send messengers throughout the nine worlds to ask everthing to cry for Balder. Everyone and everything does except one old crone who lives in a cave. She tells the messengers that she will cry dry tears for Balder, and that Hel should keep what she has. It is believed we are told that Loki is disguised as the old woman. Balder and Nanna are then forced to remain in Niflheim until Ragnarok releases them. As with most of the male written Eddas and Sagas Snorri did not feel Nanna was important enough to mention as surviving Ragnarok. But I / we should assume that she becomes Queen of Asgard after the Surt' s fires die down.
I will not go into Saxo Grammaticus' version of Nanna in Gesta Danorum, because in his version Nanna is a human who is romantically involved with the demi God Balderus, and King Hotherus, and this of course has nothing in common with our Goddess.
I was not sure whether I should add Nerthus or not to my discussions on Viking Age Goddesses. Nerthus is a Germanic Goddess who was honored even before the Common Era began. When I first entered our religion I believed to honor Nerthus and Jord seemed to me like honoring Wodan and Odin at the same time. Over the years though I have begun to see her not so much as the Goddess who is Earth, but a Goddess of fertility who lives within the soil.
The best description of how our Germanic ancestors saw Nerthus comes from Germania by Tacitus:
The Langobardi, by contrast, are distinguished by the fewness of their numbers. Ringed round as they are by many mighty peoples, they find safety not in obsequiousness but in battle and its perils. After them come the Reudingi, Aviones, Anglii, Varini, Eudoses, Suarini and Nuitones, behind their ramparts of rivers and woods. There is nothing noteworthy about these peoples individually, but they are distinguished by a common worship of Nerthus, or Mother Earth. They believe that she interests herself in human affairs and rides among their peoples. In an island of the Ocean stands a sacred grove, and in the grove a concentrated cart, draped with cloth, which none but the priest may touch. The priest perceives the presence of the goddess in this holy of holies and attends her, in deepest reverence, as her cart is drawn by heifers. Then follow days of rejoicing and merry-making in every place that she designs to visit and be entertained. No one goes to war, no one takes up arms; every object of iron is locked away; then, and only then, are peace and quiet known and loved, until the priest again restores the goddess to her temple, when she has had her fill of human company. After that the cart, the cloth and, if you care to believe it, the goddess herself are washed in clean in a secluded lake. This service is performed by slaves who are immediately afterwards drowned in the lake. Thus mystery begets terror and pious reluctance to ask what the sight can be that only those doomed to die may see.
Though I do not " feel " Nerthus in the way that I do the other Gods and Goddesses in our pantheon, I have always honored Mother Nature as a Goddess without giving her a name. As I have moved down the religious path known as Asatru I have more and more recognized that these two are one and the same. Nerthus is a powerful Goddess of fertility who can enrich the soil or in anger blow up winds that can destroy crops and farmsteads. She is a Goddess that should always be honored and made happy.
Go with Odin' s wisdom, Freyja' s love, and Thor's protection !