A thermal bridge is created when materials that are poor insulators come in contact, allowing heat to flow through the path created. Insulation around a bridge is of little help in preventing heat loss or gain due to thermal bridging; the bridging has to be eliminated, rebuilt with a reduced cross-section or with materials that have better insulating properties, or with an additional insulating component (a thermal break)

When insulating a basement wall with foam insulation, leave a space behind the studs, allowing the foam to provide that thermal break between the exterior wall and the stud.  If using batts,  put a layer of polystyrene insulation board along the exterior wall before you put up the studs and batt insulation.

By insulating the walls of your pre 1970 home with airkrete foam insulation you can save up to 50% of your heating and cooling bills.  Results have shown an average savings on older homes with no wall insulation and 2×4 wall cavity of 30%-35%.  Airkrete is the only insulation that can be injected into the wall cavities of Double Brick, Brick and Block, and Block walls.   It can be installed in walls where minimal fiberglass (usually R7) is already installed as it will compress the fiberglass and fill the void with airkrete.

Weatherstripping prevents air from leaking through gaps around doors and the moving parts of an operable window.

Weatherstripping should be easy to replace. To be effective, it must close gaps completely.

Weatherstripping should be flexible and spring back to its original shape. It should allow you to open and close windows and doors easily.

Weatherstripping can be applied to the tops and sides of any door frame.

V-shaped weatherstripping creates an excellent seal by making contact with the edge of the door. It maintains a good seal even if the door warps.

At the bottom of the door, apply weatherstripping to either the sill or the door itself.

When weatherstripping your door, use a durable material that can withstand traffic but is flexible enough to adapt to changes caused by humidity and temperature.

http://www.healthandenergy.com/sealing_air_leaks.htm

This article has a fair bit of information on air sealing your home.

Electrical outlets are a huge source of drafts entering your house.  By installing foam gaskets (available at most hardware stores) behind the cover plate, you will limit drafts from getting into your home through these areas.  In addition to the foam gaskets, you can also put the plastic safety plug covers in each outlet.  This will serve 2 purposes, to keep children safe from unexpected shocks, and also seal the plug holes, which can allow drafts also.

Cellulose, and Airkrete foam are a couple of  the most common types of blown- and sprayed-in insulation materials in the retrofit market in. And it is worth it. Retrofitting insulation into existing walls and attic space can achieve a 20 to 30 percent savings on heating bills. The learning curve and the inconvenience factor make most other blown-in applications impractical for a homeowner, and spray-in insulation should be left to the pro.
Cellulose is composed of up to 85 percent recycled newsprint. The remaining content is commonly a mixture of borate and ammonium sulfate that functions as a fire retardant. These chemicals also deter rodents, insects, and mold.   Avoid materials containing formaldehyde and mineral fibers. Dry cellulose is very popular for blown-in insulation applications. Cellulose’s small particles fill voids and corners well as the material is shot into the walls. Dry cellulose offers an “itch free” installation, but respirators and safety goggles must be worn during the process. Cellulose dust is fine and tends to take a long time to settle.

Airkrete cementitious foam is a magnesium-based product that is derived from seawater. Because of its consistency, foam is the most effective product for retrofitting into existing walls. Foam will work its way around any obstacle, providing a near-100 percent wall fill (cellulose, for example, may not fill completely around bundles of wires or pipe runs and leave random voids). Unlike bottled foam insulation used to seal small gaps around pipes and wiring, it does not shrink or expand.   Airkrete cementitious foam is the most costly insulation to retrofit, but is the most benign in regards to indoor air quality; when it is being applied into a wall there is no dust.

It is important to note that most homes in North America have substantial air leaks which can cause poor energy efficiency throughout the home. Many of these air leaks can be rectified quickly and cost effectively by paying attention to the major players, exterior doors and windows. More times than not, an air leak can be fixed with a simple door jam or caulking in a window frame.