If the estate tax is your main concern, consider a life insurance trust rather than owning the policy in your name. Your agent will probably push you toward a permanent policy, because it's much more lucrative for him. However, these policies do have their merits. A term policy, as the name implies, is good for a fixed number of years, usually ten. The premium is often guaranteed to stay the same for five years, but it goes up as you age.
Term insurance is pure death insurance.
That is, you pay the premium, and the insurance company pays off if you die. Unlike a permanent policy, this has no cash value. Term insurance is relatively cheap. The premium will depend on your age, your health history and whether or not you're a smoker. Try to buy it as part of a group plan such as a professional trade group or a college alumni association.