These are my favorite Crocs--nice and warm and cozy, plus they're easy to slip into and out of. Yes, they look like...well, clown shoes, but even if they make an awkward fashion statement, I don't care. I wear them all the time during cool weather.
If you're thinking of getting a pair of fleece-lined Crocs, make sure you purchase the models with black or dark fleece. White fleece gets dirty quickly and is tough, if not impossible, to clean and maintain.