I once checked out a book from the library called "The Tea Tree Oil Bible" by Elvis A. Ali. I actually did not read much of it before it had to be returned. It looked great, though!
I'd love to get more creative with essential oils.
I use Tea Tree oil for cleaning (a few drops combined with water, vinegar, Citrasolv), as a disinfectant (make a salve w/ unpetroleum jelly, a rinse for toothbrushes w/ water and a drop.) Lavender goes in the bath, in cleaning solutions/laundry. I make a chest salve from eucalyptus oil and unpetroleum when my kids are congested. I have also used all three of these oils (not at the same time) in a steaming hot bowl of water when I have a respitory illness. I lean over the bowl, cover my head w/ a towel, and breathe in the healing vapors!