The best two acid combo's i know of are LSD with oral cannabis and LSD with passionflower.
Oral cannabis is absolutely fantastic with acid. Much better then smoked cannabis. You'l have very spectacular visual effects, an immense sense of euphoria and a strong enhancement of the psychedelic effects of it.
Passionflower is even better. The LSD becomes a psychedelic that's fully equal to DMT, this way. But it still remains it's own unique character. The effects of this combo are very hard to describe because they totally surpass those of plain LSD, but are different from the effects of any other psychedelic this powerfull.
Datura is very synergistic as well and indeed also nux vomica.
I don't like alcohol with it that much, although the effects are funny. It makes you feel incredibly strong.
Fly-agaric has a good synergistic effect as well in moderate doses.
Another thing that's very nice: a large dose of LSD first, and on the come-down a very small dose of it again. It's the best cure against the fatigue at the end.