It's so hot right now that I went sans jacket but for cooler temps I think a grey cardigan would look great with this ensemble. (jeansandateacup.com)
Also, lest you think it's nice enough outside to commute to work sans jacket, here's what I actually wore on my windy walk to the train. (looplooks.net)
The temperature was amazing, and I pretty much went half the time sans jacket / coat. (styleoptimist.com)