Most commoditites/futures broker do not offer interest-bearing accounts. In a way, IB does the right thing by not getting involved with MM accounts--look what just happened to the MM business--it needed bailing out. I have started to invest in preferred and investment grade bonds as a way to boost current income. Margin required is only 1/3 of equity, instead of the traditional 1/2, so I can't complain. Since I have the cash to cover the investments, there is no interest charged. Food for thought.