Given the abundance of 'sample material' I had to offer during my last elaboration on the topic of aural aids, I thought it most effective to give said material its own entry, so that I may divulge the entirety of the content available. The following suggestions, comprised mainly of songs/soundtracks (with a brief entry regarding sound effects), shall be categorized into the three most general campaign settings I could imagine, and presented with as little personal bias on my part as I can muster.
Setting: Past (Medieval Fantasy/Medieval Reality/Prehistoric/etc.)
-Chaos Legion (Soundtrack)
-E.S. Posthumus (Artist)
-Dead Can Dance (Artist)
Setting: Present (Fantasy/Realism)
-DJ Amuro/Taka (Artist)
-Metal Gear: Solid Series (Soundtrack)
-John Williams (Artist)
-Viewtiful Joe (Soundtrack)
Setting: Future (Space-Faring/Apocalypse Planet/Dystopian Civilization)
-Phantom Dust (Soundtrack)
-Zone of the Enders (Soundtrack)
-Armored Core Series (Soundtrack)
-Daft Punk (Artist)
Setting: Misc. (Selections don't fit a specific period/may be used in multiple settings)
-Adya Classic (Artist)
-The Big O Anime (Soundtrack)
-Yoko Kanno (Artist)
-Two Steps From Hell (Artist)
-Immediate Music (Artist)
-Hans Zimmer (Artist)
For those in need of additional material, I urge you to look no further than your favorite theme-appropriate form of entertainment. Whether it's a movie (Lord of the Rings), game (Call of Duty Series), or anime (anything by Hiyao Miyazaki really, you can't go wrong as far as music is concerned), chances are, an official soundtrack (OST) is available for your enjoyment and subsequent use in a later session.
If you found a particular time period to be meagerly represented or completely absent from this list, feel free to take the initiative and research the sort of music typical of said time (Big Band, Classic Jazz, Baroque, etc.).
Due to the highly situational nature of these provisions, I find myself unable to supply an adequate suggestion for you, the reader. However, I can advise you to start your search with 'soundboards'; a collection of different phrases, voices, or other audible effects stored and centralized in one program or page. While they're most notorious for impersonating certain celebrity speech patterns, a search of reasonable depth can yield a variety of offerings at one's disposal.
Last, but certainly not least, a collection of specific songs that hold a certain amount of sentimentality to myself, which shall be elaborated upon per entry.
During one of my few Horror/Suspense games, I had used the repetitious mid-sections of the song to signify the appearance of a particularly horrendous monster. The volume would be raised or lowered, depending on how close it was to them. Great psychological weapon; the song really did live up to its name.
Used during a Sci-Fi campaign as an intro for an A.I.-gone-wild/cyborg boss battle.
One of the (very) few session-compatible Rap songs in existence.
A running joke, of sorts, in my group. No matter the campaign, whenever the PC's enter a bar/night club-esque environment, this song will always play on infinite repeat until they leave. : P
One of the first songs I've ever used in a session: impending battle + victory theme, all in one package.
Generic church/sacred ground music, at first...
...and when things hit the fan. The look of surprise on the faces of the PC's was priceless as they scrambled for their equipment in what they believed to be a 'safe' area.
...Just making sure you're still paying attention.
Some ballroom music, also doubles as 'peaceful city' music whenever I need to establish a calm, neutral mood.
A little modern music, for when I need to break up the monotony of 'medieval' music. It also worked well when the PC's looked upon a strange, exotic landscape (I skipped the intro vocals for that one).