Like most churches we hold a VBS and the youth participate. But we took it a step further. We have an X-Treme Team, which is a group of youth who come in on Sunday evening and stay through until the end of the Friday night program. They live at the church as a missionary team. They cook their own meals, clean up after themselves, and serve preping the materials for the next day. During the VBS they work directly with the children. When the VBS is over, the X-Treme team goes swimming (our church does not have showers) and gets clean. After swimming and lunch, the Team spends the afternoon and evening being discipled. We visit local areas that have devotional qualities (museums, rock-climbing, historical sites, parks, natural attractions) We incorporate all of the ideas of a mission trip (daily quiet times, worship times, teachings) plus we address feedback we get from the adult helpers at the VBS.
Since we are still at church we have youth group as normal and have lots of hang time with our students. We are going to be exhausted by VBS anyway so we thought why not make it a Youth mission as well.