I found a couple old threads, but I think 9v is ready for a less general more detail thread. Seems like there are three basic types, Ni-Mh, LSD Ni-Mh, and Li-on. First two types are typically 9.6v fully charged, and the Li-on 8.4v (2S).
What I would like to do is fill a chart with;
Brand / Type / Charged volts / Claimed Mahr / Actual MaHr / Comments like charger used, issues, odd physical size.