I don't know what the weather is like where you live, but here in Denver it's been as indecisive as yours truly standing in front of a French pastry display. One moment, I'm flip flopping around town, enjoying the sun and the next I'm caught in an Arctic blast (okay, so it's still 60 degrees, but still, that is practically freezing). My solution - the always versatile, easy-to-carry cardigan.
Cardigans are one of those rare fashion pieces that work with just about anything (you can't say the same for, say, a hot pink feather boa, for example, or can you?). Skirts, pants, shorts, dresses ... All can benefit from the simple cardigan. I usually recommend clients buy several - one cream or white, one black, and one in a vibrant color (I love this season's orange - it matches everything) so that you have a ready option to grab on your way out the door.