Some of you might find this guitar book useful. Of course, it is for six string guitar, but it covers open tunings and playing slide guitar. Should be fairly simple to translate to CBG. I am about to print out a copy for myself.
After reading the first few sections, I can honestly say this is one of the better beginner books that I have seen. The author starts you out in Open G tuning so that you can just play bar chords and focus on strumming and rhythm. The teaching style is very laid back and focuses on folk/country/blues style songs. So far I am enjoying this book.