When Melanie Charest and I first planned an inquiry course, we created 4 different types of inquiry. This is just our brain child, and there are many books that tell of many different ways (see below for what we have in our library). The idea is that children can inquire by learning a new skill, learning about something, inventing something, and solving a problem. We have slides, plans, and handouts for all of these. Please come see one of us if you are interested.
Also, Brodie Maundrell uses open inquiry in his SS9 class. He is a great wealth of knowledge and a great collaborator.
The Power of Inquiry is one of my favourite books. It talks about making inquiry a part of your classroom culture. Great little tips and tricks in this one.
Trevor MacKenzie is popular with many of our colleages. He describes inquiry in 4 levels. Good for those who like to start with manageable chunks.