Black Cohosh

At a wild guess (I'd never heard of the stuff), there's next to zero research, and any benefit is no more than snake oil. Google tells me that many people are getting rich on the stuff, which also suggests it's unlikely to have nasty side effects. Probably won't hurt to try it, if you have the spare cash to take the bet.

And a quick search of Pubmed found one small study, which found black cohosh's effects  "not significantly different from that of placebo".

A Cochrane review (an overview of the available research) found:
"There is currently insufficient evidence to support the use of black cohosh for menopausal symptoms. However, there is adequate justification for conducting further studies in this area. The uncertain quality of identified trials highlights the need for improved reporting of study methods, particularly with regards to allocation concealment and the handling of incomplete outcome data. The effect of black cohosh on other important outcomes, such as health-related quality of life, sexuality, bone health, night sweats and cost-effectiveness also warrants further investigation."