Please note I did not check any of the licenses for the following sites, that's your job... thread starter. Nor did I check that the sounds are in the correct format for use in map creation, again, this is for the thread creator.
Here's a list of Free Sounds sites:
Sounds:For the User: You may use the sound effects on this web site free of charge in your video, film, audio and multimedia productions (but do not re-sell them or post on a web site for download).
http://www.pacdv.com/sounds/index.htmlThis site isn't really good at all, the best this site can offer is limited amount of sounds you can use.For the User: You find the license.
http://www.thefreesite.com/Free_Sounds/This site seems pretty good, i've heard alot about "thefreesite" but I havn't really used it.For the User: You find the license
http://simplythebest.net/sounds/ I personally would recommend this site (if the license checks out). I've taken a few sounds from this site and was surprised by the diversity and quality of what the site has to offer.For the User: Creative Commons
http://freesound.iua.upf.edu/Thought I might just mention this one 
For the User: Wav format, you may use these sounds for free.
http://amazingsounds.iespana.es/en/This one seems promising but I haven't really checked it out-------
Btw as Thorn said, here's a great link for textures >.>
http://tremmapping.pbwiki.com/Textures+and+Skyboxes
