Modern Influence of Norse Mythology
The Lord of the Rings and Norse Mythology
Interestingly, J. R. R. Tolkien was a huge Viking enthusiast. He translated a copy of the Volsunga Saga himself as a young man, and later formed a "Viking Club." This influence can be seen readily in his work at almost every turn. The Dwarves, Elves, and Orcs all seem to draw heavily on the myths of Scandinavia, and in fact are almost identical to the races of the Sagas. Dwarves are mountain-dwellers, short in stature, bearded, and known for their blacksmithing and craftsmanship in both instances, for example. Light Elves are equally identical in description, with Rivendell drawing strong parallels to Alfheim.
The Balrog Durin's Bane, as encountered in the mines of Moria by the Fellowship of the Ring, has his roots in Sutr the Fire Giant and ruler of Muspelheim. Even the destruction of the bridge of Khazad-dum mirrors the destruction of Bifröst, the bridge to Asgard. The One Ring itself may be derived from Andvaranaut, a magical ring cursed by Loki to bring destruction to whoever owned it.
Gandalf is frequently associated with Odin, who often travelled the world of men as Vegtam the Wanderer, an old man in a cloak who carried a staff. Gandalf, like Odin, serves as a guardian of mankind and is a source of power, wisdom, and great faith in humanity.
Were you aware of the Lord of the Rings' correlation to Norse mythology prior to this?
Harry Potter and Norse Mythology
While Harry Potter derives a number of now-common fantasy elements attributed to the influence of Tolkien, those drew directly from Norse mythology. Elves, Dwarves, and Trolls are all synonymous with fantasy fiction today and come directly from Northern mythology. Still, Rowlings Harry Potter seems to have been influenced in a somewhat broader sense.
For example, the werewolf Fenrir Greyback is obviously named after Fenrir, the father of all wolves, from Norse mythology. There are a number of other elements which could easily be correlated between the two subjects, but it is difficult to say whether Rowling drew on Norse mythology or just commonly established themes in the fantasy genre. That will have to be left to speculation.
World of Warcraft and Norse Mythology
In the PC game World of Warcraft: Wrath of the Lich King, many characters and environments are pulled directly from the world of Norse Mythology. Utgarde Keep in WoW, for instance, is an obvious draw from Utgard, the stronghold of the Giants in Jotunheim. Loken, a boss character in the game, has a brother named Thorim obviously derived from Thor, and a sister-in-law named Sif, the wife of Thor in Norse mythology.
The Lich King employs a race of spectral creatures called "Val'Kyr", winged female "battle-maidens". This is obviously in reference to the Valkyrie, female warriors who serve Odin in Norse mythology and collect half of the warriors who fall valiantly in battle (the Einherjar), bringing them to Valhalla in preparation for Ragnarok.
Halo and Norse Mythology
Both in the game itself and in the novelization thereof, there are a number of references to Norse mythology within the prolific shooter Halo. The main player character Master Chief, for example, wears a special type of armor called MJOLNIR, the name of Thor's famed hammer.
In the Halo novel Contact Harvest, a number of locations and characters are named after Norse mythology, including Loki and Sif as artificial intelligence entities and locations such as BiFrost and Utgard.
This is a broad scope, as many bands have taken on a Norse theme in their work. Bands such as Manowar, Tyr, Amon Amarth, Therion, Leaves' Eyes, Doomsword, and Bathory all draw heavily from the Vikings, and in fact Viking Metal is considered an accepted sub-genre within the metal world. For something a bit less aggressive, Richard Wagners Der Ring des Nibelungen is based in Norse mythology.
Wardruna deserves special mention. A Norwegian project, Wardruna is a group drawing from the Runes of the Elder Futhark to inspire exceedingly unique music. The project was started in 2003 by Einar Selvik, Lindy Fay Hella, and the now-notorious Gaahl, former front-man of Gorgoroth who was popularized as one of the faces of Norwegian Black Metal.
This one is by no means definitive. I would love to get some suggestions for other subject matter to look into, so please feel free to comment.