I'm with the crowd that says for your commute you don't need anything bike specific. Better to spend your money on general purpose outdoor clothing that you can use for your life off the bike as well as on.

If you absolutely must have something bike specific I recommed a goretex helmet cover- not cheap -but I think available below MSRP on line.

http://www.gorebikewear.com/remote/S...1208436871979A

I hit the road at 5AM for a 9 mile bike commute to the train. That means pretty much hopping out of the shower and onto the bike with a wet head. Below 25 degrees I use the helmet cover and it makes a world of difference. Also keep it in my bag in the summer to stay a little drier in those downpours.