I'm thinking of making a Spotify playlist with music to listen to while playing RPG's without much in the way of music. Spiderweb games, roguelikes, stuff like that.

Anyone have any suggestions for soundtracks or specific artists? I'm looking for mostly instrumental, but the odd vocal track wouldn't be terrible.

I assume this is about downtempo ambient?

Above & Beyond: Eternal, Filmic, Sun In Your Eyes, Tri-State, In The Past
Solarstone: Destination (Update Project Ambient Mix)
First State: My Sanctuary

You could also search for Armada Lounge, pretty beautiful compilations.

The Lord of the Rings soundtracks were what first came to mind.

Conan: The Barbarian (original movie) had a pretty fitting soundtrack.
And you can't go wrong with "borrowing" the soundtrack from other games. Icewind dale, Guild Wars, specific tracks from Daggerfall, the soundtrack from Crusader Kings 2, Ultima 7 & 9 all have "useful" soundtracks.

While not really ambient music per say, Hawk, I enjoy playing RPG's while listening to a lot of Final Fantasy soundtracks

I'm not really knowledgeable about ambient music. It's not super-ambient, but The Flashbulb is a good instrumental electronic band. Sigur Ros is pretty ambient despite having vocals.

Some of my favorite game soundtracks are (no idea if you can find them on Spotify): Arcanum, The Last Express, Grim Fandango, The Longest Journey, Bastion, Superbrothers Sword&Sworcery, Folklore, and Shadow of The Colossus. Mark Morgan's stuff (Planescape Torment, Fallout) is good if you want something more atmospheric.

Midnight Syndicate, Nox Arcana

edit... Oh, the soundtrack to "Legend" by Tangerine Dream is quite good too.

By ambient I meant more "meshing with the game" rather then the genre.

It honestly never occurred to me to use the soundtracks from the games I own on GOG. So that's a pretty good first step.

I'll also try out the artists/soundtracks suggested.

I love rougelikes, from the original Rogue to Angband and some fun new stuff like DoomRL or AliensRL. I have a few CDs from a band called Crash Worship that I like to listen to while playing. It's sort of Industrial/Tribal so it might not be what you are looking for but I like it. I actually like listening to the LOTR sound track while playing Mount & Blade.

Planescape Torment soundtrack or Enya music.

I normally prefer to keep the music from the game, so when it's terrible or missing, or just starts to grate on me, I use it as an excuse to catch up on an artist I enjoy but neglect listening to.

Asheron's Call had no music, so I always play it to Robert Rich. Now his music gives me pangs for old Dereth.

Tabula Rasa and City of Heroes had such miserable music I shut it off and got acquainted with Echospace & Von Schommer. This is nice mellow stuff for a more urban or technological setting.

For my recent foray into Minecraft, I mainly listened to Oophoi and Algol. The Algol track "Cosmic Elegy" is pretty incredible for relaxed travel or exploration in an exotic locale.

If the game has an ancient or desert setting, I'll start a Spotify or Pandora station with Sarband or Sequentia, which are period music ensembles.

I remember thinking as a kid that Secret of Evermore's soundtrack was amazing for its time. Drew me in so much with the awesome sound effects and the whatnot.

The Age of Conan OST. Some are good ambient tracks, but most aren't. Just filter them out if you get your hands on them.

http://www.youtube.com/watch?v=Efl_PNTvPmU

hey, don't know if anyone already said, but listen to this band...
Blackmore's Night..
By Ritchie Blackmore.. ;p