I like my Sierra Designs Microlight jacket. It comes with it's own stuff sack. Packs down to the size of a soda can, just a little thicker. It's extremely light and has a hood. It lives in my messenger bag that I carry to work and is always ready to get worn if the weather gets nasty. My daily commute is a 30-minute walk.

Sierra Designs Microlight jacket

It sells for 32$ MSRP. Although I love my 300$+ Gore-tex XCR Arc'teryx jacket for mountaineering, this Microlight gets the job done for my daily commute!

Highly recommended.