hi,
drivers/power/twl4030.c has a twl4030_power_init() function which is called by most (all?) OMAP3 boards. What it does is enabling VAUX3, VPLL2 and VDAC power supplies in TWL4030/TPS659x0 chip. However they are all very board specific and in most cases not needed at all, at least for booting the kernel. They also cause regulator warnings on latest kernels.
VAUX3: board specific, beagle doesn't have it connected at all, so it wastes power there. VPLL2: board specific, typically display related, as mainline u-boot shows no graphics I think it can be removed. VDAC: typically used to power TV-out DACs, can be removed. VDAC and VPLL2 is already handled by kernel by DSS2.
So I think VDAC, VPLL2 can be safely removed, probably VAUX3 too with whole twl4030_power_init().
GraÅžvydas