I wear a Patagonia Houdini pullover. It has pretty good wind resistance and is positively tiny when packed into its pouch, perhaps the size of a couple of decks of playing cards. I just leave it on my bike all the time. If you're looking for something with an added liner, or for the rain this probably won't work. Arc Teryx makes a nice one too, but it's kind of pricy for such a thin garment at about 170. I have one of their gore Tex models for wetter weather, but rarely ride in the rain.