Foam is great but expensive. Look into Cellulose insulation in your attic and walls.
I've had cellulose in both of my homes and each job has paid itself off in energy savings within 3 years. If you are building a new home for yourself, or plan on being in a home over 5 years, it is worth the investment.
Bonus: The Sound isolation is also great.
If you are interested in the St. Joseph or KC Northland:
http://brandtsfuelsavers.com/insulation/4710456