RBC Ministries offers free Bible studies, devotion booklets, and Christian courses. I use Our Daily Bread everyday. I like it better than other devotionals because of the amount of scripture in each lesson. Rather than one verse and the rest commentary, it includes one page of a portion of scripture and one page of commentary. Sometimes I don't even read the commentary. It's like reading the Bible in chunks!
I've also used one of their Christian courses and love it! As of February 2009, you will be able to take the Christian courses for certification for a fee of $20/CEU unit. I would use this as a high school credit in Bible also. Highly recommended. The materials are written by Christians of many denominations. You can read their biblical principles here.
If you use their materials, PLEASE, send them a donation now and then. God would want you to!