These I really liked. Designed specifically for snow sports and featuring a boot cut (which means there's no danger of them rucking up inside your boots) Patagonia's Boot Bottoms combine R1 fleece to keep your knees and bum warm and Capilene 4 fabric panels elsewhere for breathability.
The fit is snug and even supportive around the knees and you can feel the warmth the minute you slip into them; the seams are flatlock for comfort and unlike some synthetics Capilene doesn't retain odours if you don't wash it for the entire length of your ski holiday. Although designed for skiing and boarding I'd be happy to use the Boot Bottoms for other cold weather activities and they're versatile enough to be worn with both shell and insulated ski pants.