Feet

dot_clear.gif (42 bytes)Feet are one of the first parts to suffer from the cold while cycling. They are a long way down the blood distribution system. They are whizzing around in the breeze, making a really thin boundary layer of cold air sucking out heat. Wearing extra layers of socks usually restricts blood flow to the feet, making matters worse.
dot_clear.gif (42 bytes)

At temperatures over about 30 degrees F a pair of lined booties over summer bike shoes may work. That cutout for Look or SPD style clips lets in considerable draft. I f you have an oversized pair of shoes, you're in luck.  You have room for   an

extra pair of wool or poly socks (no cotton!), and a chemical toe warmer. That may get you to about 20 degrees F.(The chemical warmer is a fine secret weapon. At about $1 a pair, it will last for hours.) For most folks, booties over summer shoes just don't work at temperatures much below freezing.
One step up from the booties is to kludge something from any well insulated boot, using oversize mountain bike cages on a conventional clip pedal. The treads will drag on the pedal, but the feet will be warm.
But far better, take Simon's advice on boots. L. L. Bean's Snow Sneakers are light weight and nicelyLL Bean Snow Sneakers with cleats insulated. They have a low profile tread that makes for a good mounting surface for SPD or Look cleats. SPD cleats can be mounted by drilling the sole and screwing the cleat into a SYNTACE SPD Adapter (Colorado Cyclist Cat. # SNT-MXA-1, $17). But a Look style cleat can be mounted even more securely. It can be attached to T-nuts (see your bike shop) under the insole with 5mm X 0.8 20mm screws, available at your hardware store. Those screws are almost long enough to engage the nuts, so it takes some messing around to compress the assembly enough to get them started. Then, some screws will extend a little beyond the nut - but with the insole replaced the foot should not contact the screw, which will reside in a depression. Mount the cleats with care so that the wider boot sole will clear the cranks. Buy your boots oversize to accommodate a couple of pairs of heavy socks and even a chemical warmer.   (Oversize: At least two US sizes, 5 European sizes.)
Ready made Winter bike shoes: SIDI has waterproof/windproof boots, Storm 2, (mtb) for about $190. They'll work with any clip design. The insulation is poor, so get them 'way oversize to accommodate bulky socks and heaters.
http://w Do check out IceBike, the best Winter cycling source on the web, for much more information.