I frequently see new vendor-specific properties being used, what prompted this question was seeing -moz-appearance:button;
somewhere (makes the element look like a button).
Where can I find a list of all these extensions (vendor-prefix rules)?
Mozilla has one, Opera has one, there's an "unofficial" one for webkit (tho it doesn't explain the properties). I had no luck for IE. If there's not one all in one place, an official, comprehensive list for IE and webkit would do.
This one is great:
http://peter.sh/experiments/vendor-prefixed-css-property-overview/
Sitepoint also has a decent reference:
http://reference.sitepoint.com/css/vendorspecific