http://store.caig.com/
Not just any 'contact cleaner'...this stuff really works. I recommend it personally. The regular DeoxIT should be fine for most car applications. You can buy at Radio Shack but they sell it online now and you can buy larger sizes at a discounted price. Unfortunately they do have a $25 minimum for online ordering.
Down under the forums there's an interesting post from a Mercedes owner...about 2/3s down the page on the left side.