Looking for info on mtDNA variation and stratagies for detection

[John E. Stacy]

I want to know if anyone out there has experience with (vertebrate) mtDNA -
In particular, how much intraspecific variation is there in the "D-loop"?
Regarding intraspecific variation, is it all at the level of single base 
changes, or are there length variations (i.e. detectable as PCR product 
length variants).

All comments and references greatly appreciated.