If you are looking for links to a database of sounds, in addition of the other links that you will found with this requets in a search engine, you can have a look to the following sites:
(this list of links is from knarfworld)
http://www.findsounds.com/
a search engine with sounds to the formats AIFF, AU and WAV.
stonewashed
an index of sites with link to several base of sounds.
http://www.grsites.com/sounds/
A database of sounds.
And a site with a lot of ads, with sounds of cars:
http://enginesounds.free.fr/