Here's some more:
Samples
www.killerbeats.com/sounds.asp
Killer. Beats. Possibly.
www.bbc.co.uk/radio1/onemusic/studio
BBC collection.
www.loopasonic.com
Free login required.
www.djsamples.com/djsamples/freesamples/
Samples for DJ.
www.superloops.com/listen.htm
Check those crazy categories
www.breakbeatsonly.com/preview1.htm
Pro site with some freebies.
www.zero1media.com/samples.htm
Short hits and loops.
www.naturalstudio.co.uk
Acoustic drum kit and other instruments, high quality.
www.sonichound.com
Drums and synths.
www.electronisounds.com/Wav_CDs.html
Sample CD site with demo packs.
www.hollowsun.com/vintage/index.html
Vintage keyboard and synth sounds
www.modarchive.com/waveworld
Drums, synths, pretty much everything.
www.proloops.com/freeloops.asp
Pro site with some free loops.
www.analoguesamples.com
Analogue samples.
www.glooped.com
Guitar samples.
www.herman-witkam.com/raw/
Unusual instruments. Need to email to get user name.
www.studiothirteen.com/Sample_Page.htm
Eclectic.
www.grsites.com/sounds/
Absolute Sound Effects archive.
www.hollywoodedge.com/samples.aspx?SID=7&
Various Hollywood FX.
www.soundamerica.com
Low quality, but where else are you going to find a vomiting cat?
www.a1freesoundeffects.com
A1 free sound effects, just like it says.
Other stuff
www.history.com/media.do
Classic speeches from the History Channel.
www.geocities.com/CollegePark/3812/tubesounds.html
Underground voices. As in "Mind the gap."
www.dailywav.com
TV dialogue, and lots of other stuff.
www.thebots.net/GWBushSampleArchive.htm
George Bush samples.
www.archive.org/movies/prelinger.php
Advertising, educational and industrial film archive. Fascinating.