Our middle schooler's have a prayer wall - a painted mural of concrete blocks on the wall. The kids can offer prayers using colored post-it notes stuck on the wall.
Prayer Rope with Prayer Tales
We also have a prayer chain. A colorful braided rope that we hold during prayers (so we don't have to touch each other!!) We have prayer "tales" attached. Each youth made a macrame and beaded tale to clip to the prayer chain. At the end of the year they can take the tale home as a reminder to pray.