Trip Barber of the NAR sent out a newsletter talking about the new Federal Rocketry Rules dated Dec 4, 2008.

Trip writes: "The biggest change affecting the largest number of NAR members is that the category of "model rocket" is expanded up to a liftoff mass of 1500 grams and no FAA notification of any kind is any longer required for launches of model rockets up to this limit. Previously notification of the FAA was required for "large model rockets" over 453 grams."

Here's the link to the Fed document:

http://edocket.access.gpo.gov/2008/pdf/E8-28703.pdf

You can jump past all the discussion and got to the final amendment on page 14 (of this PDF file).

Included is the General definitions.

Amateur rocket means an unmanned rocket that:

(1) Is propelled by a motor or motors having a combined total impulse of 889,600 Newton-seconds (200,000 pound-seconds) or less; and

(2) Cannot reach an altitude greater than 150 kilometers (93.2 statue miles) above the earth’s surface.

§ 101.22 Definitions.
The following definitions apply to this subpart:
(a) Class 1—Model Rocket means an amateur rocket that:
(1) Uses no more than 125 grams (4.4ounces) of propellant;
(2) Uses a slow-burning propellant;
(3) Is made of paper, wood, or breakable plastic;
(4) Contains no substantial metal parts; and
(5) Weighs no more than 1,500 grams (53 ounces), including the propellant.
(b) Class 2—High-Power Rocket means an amateur rocket other than a model rocket that is propelled by a motor or motors having a combined total impulse of 40,960 Newton-seconds (9,208 pound-seconds) or less.
(c) Class 3—Advanced High-Power Rocket means an amateur rocket other than a model rocket or high-power rocket.