If I'm all geared up, I usually wear a pair of tights (from a dance store) under my summer bike shorts. Usually does the job and keeps my legs warm. I wear a long sleeve under armor under my jersey, but this doesn't help too much as it doesn't really help keep out the wind. I guess it keeps my core temperature regulated.

In addition, I use a balaclava to keep my neck/ears warm, but this usually gets too hot once I've ridden a bit and I have to pull it off and suffer frozen ears. I pull on whatever windbreaker/shell I can find to keep the cold out for good.