We all need the occasional aid to inspiration for writing RPG adventures. One wellspring I turn to quite frequently is music.
Not just classical works like Holt's "the Planets", but also good old Rock&Roll.
I have three or four albums that never fail to get me inspired and many other songs have provided that little nudge.
Blue Oyster Cult's Imaginos is a campaign waiting to be played. There is so much great stuff in this album. It is a never fail source for me. The band has written and recorded with Michael Moorcock so it should be no surprise. The songs "Veteran of the Psychic Wars" and "Black Blade" are specific tributes to Elric of Melnibone. Neither of those is on this album but many other great cuts are. "The Seige and Investiture of Baron von Frankenstein's Castle at Weisseria" in addition to a long title has a great driving beat. "In the Presence of Another World" is also a great tune for RPG.
After (or before) BOC is King Crimson. "In the Court of the Crimson King" is another fantastic album for gaming inspiration. The title song just about lays out a whole campaign, complete with NPCs.
Led Zeppelin, of course, with their many Lord of the Rings inspired songs provide fertile ground.
Another often overlooked source is Genesis, especially their earlier works. "All in a Mouse's Night" is a classic. "The Battle of Epping Forest" has a Clockwork Orange sort of vibe to it. "White Mountain" from the album trespass will never let you look at wolves in quite the same way again. Then there is "The Lamb Lies Down on Broadway" the lyrics and liner notes of this extravaganza are very rich in source material indeed. The Chamber of 32 doors, the Colony of Slippermen, the Carpet Crawlers have all shown up in games, as have the Lamia and the Supernatural Anesthetist. I wrote a monster description for teh Squonk based on the song of the same name. Shippy published it in HH.
Uriah Heep although sounding somewhat dated these days (OK a lot dated, but I still like them) have many songs dealing with fantasy subjects. The album Demons and Wizards is a good place to start.
Jethro Tull offer us Broadsword and other great songs.
This should do as a starter list.