16,000 sound effects samples, free for downloading. http://bbcsfx.acropolis.org.uk/
The Sound Effects are BBC copyright, but they may be used for personal, educational or research purposes, as detailed in the license.
If you need to a sample commercially, they offer them individually at a very reasonable cost as well.
The range of sounds the BBC has used is staggering. I mean who couldn’t use the sound of a single five inch pump operating with start and stop. (Sewage pump) in their mix?
Mangle, slice n dice, extract, stretch … the possibilities are endless.