We use Discipleland material for our children through age 12. It is non-dated, so it works great in a small church. We can use the lesson for a kid that shows up one week, and then reuse it if it is a different set of kids the next week. We can also store several copies and use it whenever we feel like it, which makes it a very good investment.
http://www.discipleland.com/
For our youth 13-18 and adults, we simply use the Bible. I trust that these need to be ready to study the Bible on their own, so I do not feel that supplements are the best option. One youth class, we studied Mere Christianity by C.S. Lewis as a supplement to the class.
This summer, we will be using Regular Baptist Press and their Dino Detectives for VBS. I feel that this curriculum fits well with the theme our church is working on this year, which is basically going back to the beginnings to get the basics for the faith. Dino detectives looks at Genesis to help form a proper Christian worldview in children.
