Sound and Music

AudioBlocks.com Music, loops, and sound effects. Subscription-based, offers 7 days for free downloads, then charges to credit card, so you need to be vigilant about cancelling in time. Very aggressive email marketing and retention practices, so be careful.  
CCmixter CC--Noncommercial uses free; commercial uses Creative Commons-Licensed.
Creative Commons Links to sound and music sites with Creative Commons licenses.  
European Space Agency on SoundCloud Most (not all) audio content licensed under CC BY-SA IGO 3.0. Click work to check individual credits to be certain.  
Free-loops Sound and music with Creative Commons licenses.  
FreeMediaGoo Personal and commercial use.  
FreeMusicArchives (FMA) CC Attribution-NonCommercial-ShareAlike License.  
Freeplaymusic Free for educational use and YouTube personal use; others licensed  
Free PD Music CC-0 licensed full-length works. Many are MIDI or MIDI-esq. FAQ details exact info.  
Freesound
Creative Commons-licensed audio
Free Stock Music
Licensed but no fee royalty-free music for personal and commercial use; scroll down for categories; sign up for free account; recommended credit Freestockmusic.com
Incompetech
Music free to use, must credit owner; see FAQ
Internet Archive - Community Audio
Creative Commons-licensed and public domain audio. Also search Audio Archive, then select a specific library. Can also type in Search text box specifically for "public domain music" or "creative commons music." Then, go more granular in Topics & Subjects section on the left.
Internet Archive - Netlabels
Creative Commons-licensed music (mostly)
CC - user collaboration
Public domain audio books
 
Loopasonic CC and Public Domain  
Looperman CC and Public Domain  
Jamendo CC and Public Domain  
Magnatune CC-Independent musicians, affordable licensing  
Macaulay Library-Cornell Lab of Ornithology Largest and oldest scientific archive of biodiversity audio and video recordings. Share or link content for non-commercial, personal, educational and research purposes provided that ML is properly cited as the source  
Moby Gratis Free license for over 150 Moby tracks for independent and non-profit filmmakers, film students, and anyone in need of free music for their independent, non-profit film, video, or short. Can shorten for length only. Sign up for account; must credit as Music: [Track Name] by Moby courtesy of mobygratis.com  
music alley Music safe to use in podcasts  
Musicradar Free sample section of online music magazine. Can be used commercially, but no redistribution. Scroll down for links organized by genre. Can listen to representative samples in different instruments with bpm, then download zip.  
NASA Audio Library Public domain sounds from all manned spaceflight, orbital, and interplanetary missions.  
NASA Sounds Curated public domain sounds from historic spaceflights and interplanetary missions. Downloadable for ringtones. Check Media Usage Guidelines for exact use. Smaller collection available on SoundCloud NASA stream.  
Open Metal Cast Creative Commons-licensed metal music. Probably the only CC metal music site.  
Opsound Full songs; CC Attribution Share-Alike only  
Opuzz Fee-based, but granular down to short clips; royalty free after purchase  
Partnersinrhyme Public domain, royalty free with attribution; mainly collections on CD, but some loops and video, too  
Purple Planet Music Free download collection for personal and commercial use. Selections include bpm. Credit required: Music: Http://www.purple-planet.com. Using Our Free Music details exact use.  
Sound Jay Copyright-protected sound effects and music free for personal and commercial. Available in WAV and MP3; music including bpm and other descriptions. Terms of Use details exact use, e.g., no ringtones.  
SoundBible CC and Public Domain; WAV and MP3 options  
SoundCloud Search for CC-licensed music by searching for a track, then  clicking To listen to under Filter Results in the left nav bar, then click desired license description.
Tribe of Noise User-uploaded CC-Attribution-Share Alike music. Must sign up for free to download or upload. Pro licensing and CC+ licensing available. See FAQ and Terms for exact usage. Can search on bit rate, speed, project type, genre, and feeling, among others.
YouTube Audio Library CC-Attribution and just free to use music and sound effects for videos. All are downloadable. Easy copy & paste attribution info included. Can search by genre, mood, instrument, and duration.  
YourBeats CC-licenses Attribution-Non-Commercial loops   
Library of Congress Public domain and copyrighted works; several catalogs and special collections.

Sound Online Inventory and Catalog

The American Folklife Center

I Hear America Singing


Song of America Tour