TEC is a great group that holds Catholic retreats for youth (usually ages 17-23). I attended a TEC retreat when I was in high school, as did my brothers. One of my brothers was quite active in the group, returning several years to help as a part of the retreat team. We had Mass every day, confession, and there was always a priest present the whole weekend who was the chaplain for the group.
The quality of the retreat/group may depend a bit on the particular area or region, but I think that they are mostly uniform in format. I know of many good, quality Catholic friendships that arose out of those retreats, and even marriages that happened because people met their future spouses there.