http://www.target.com/c/-/-/N-v41nu?...cyclesave20on\
You bring your old carseat or booster to Target, and they will give you a coupon for 20% off a new seat.
They sell Graco, Chicco, Baby Trend, and other moderate price brands. If you don't see a seat you like in the store, you can use the coupon on their website.
We just traded in a very worn toddler car seat for a high back booster. With a sale, the coupon and my Target RED card, I got a $50 Graco booster for $34 plus tax.