Hi A. - there are a lot of great preschools in Parker. Your choice will depend a lot on your goals for your child.
If you want a Christian preschool, Southeast Christian is terrific. My son attended there for several years. The teachers were wonderful and my son went to kindergarten well-prepared even though he had just turned 5 when he started. Parker United Methodist, Joy Lutheran, PEPC and Ave Maria all have preschools too. My youngest attends preschool at our home elementary school and is absolutely loving it. My son's student teacher ratio at the public school is 5:1
There are also great learning programs at The Goddard School, Primrose, KinderCare and Sunshine Preschool and others. Most seemed to be geared toward full-time care which I didnt need so I didnt go that direction.
You are right to start looking for preschools now - you may find the Christian preschools have a waiting list already for the 2010/2011 school year.
Best of all things!