The University of Denver CITY (Center for Innovative and Talented Youth) is part of the national talent search network.  My son (DS10) went to their DISCOVERY program (for talented 4th-6th graders), a one-week, residential institute at the University.  He took a course (Geometry & Puzzles) and lived in the dorms.  He loved it and wants to go to the two week session next summer--FRONTIER is for 6th-8th graders.  They also have the 3 wk long PIONEER program for 8th-10th graders.  I was glad to have him be able to attend a shorter institute, because of his age, since all the Johns Hopkins ones are 3 wks long. 
DS12 and DS13 attended 3 wk-long Johns Hopkins CTY summer programs at different campuses.  They both absolutely loved their experiences.  Only DS13 had ever done a program like that before, but this one had enormous diversity of students--JHU seems to have a stronger scholarship draw.  They both want to do another institute somewhere next summer, but will select it based on the course, whether it's through CITY, Duke, JHU CTY, etc.