This is a question that comes up a lot -- unfortunately the answer is that there aren't a lot of sources out there. What information has been compiled is usually either proprietary (i.e. providing a competitive advantage for consultants and companies) or has become part of a commercial training course.
OTM's online help is likely your best source and looking towards training partners is another option:
http://www.otmfaq.com/forums/f63/otm...g-options-870/ (OTM Training Options?)
I suggest checking out this section of the site for more details:
Training, Certification and Documentation - Oracle OTM / G-Log GC3 Community Support
--Chris