What you have to remember is that you don't need to dress as warmly for high-aerobic activity like cycling as you do for just walking around. Your big enemy, in fact, is going to be the wind and the rain, rather than the ambient air temperature.
So... above all, you'll need some kind of shell/windbreaker. You can also get one of those transparent plastic rain capes for when it's actually raining. They cost about $10-$15 and, since you probably won't be going out in torrential downpours unless you're ChrisL, should be enough.
For temps down to freezing, I tend to go modular -- arm warmers, knee warmers, leg warmers. Where I live [central Canada], the fall temps tend to range from very cold or cool in the morning to downright balmy in the afternoon. On a typical October ride, it might be 5C when I start in the morning and 15C when I finish around noon. Moreover, I tend to warm up as the ride prgresses. Consequently, I like being able to peel off layers as needed.
Having said that, it really does get cold in the winter, and I'll ride down to -10C [14F], or so. On a not-too-windy day, I'll wear shorts, polypropylene tights, a wool or microfleece LS jersey, polypropylene sockliners [thin] and wool dress socks [thin], a shell, full-fingered gloves, neoprene booties and a polypropylene balaclava. I'll usually double-glove [acrylyc or polypropylene glove liners under my gloes] and sometimes wear a polypropylene base layer under my jersey. On really windy days, I'll wear two tights.
Just to give you an idea, my winter wardrobe consists of three pairs of polypropylene tights [one padded, two not padded], two pairs of lycra tights, knee warmers, arm warmers, neoprene booties, two microfleece LS jerseys, a wool LS jersey, a windbreaker/shell, a slightly insulated Sugoi cycling jacket, a wind vest [GREAT investment], two polypropylene undershirts, a polypropylene skull cap and balaclava, polypropylene sock and glove liners, wool dress socks, full gloves.
This is what I looked like in March:
Fortunetaly, most of this stuff can also be used for trail running and XC skiing!
The biggest problem I have in the fall and winter is knowing how to dress for the weather. I invariably over-dress, though.