We have a little one who turns two today, and in the research I have done on preschools I found out there will be a Goddard School opening near Arapahoe and Aurora Parkway in late summer/early fall. We plan to take our little on there, but perhaps not until she is three.
I have also heard that Primrose Schools are good - there's one at Gun Club Road off of Smoky Hill and E-470.
There are MANY good preschools out there - you need to go and visit and tour the center (unannounced is best). Try to go in the early morning so that you see the program in action. If you go near lunch time or just after, most of the kids are sleeping on cots. Afternoons seem to be the less structured times for those kids staying all day - the mornings are when the classes are in session.
Hope this helps.