My wife and I were both addicted to masturbation as teenagers, and we still masturbate together a lot. Being the sort of person who likes to experiment, early on in our relationship I bought my wife a vibrator, which has become her constant bedroom companion.
A few years ago, my wife discovered that she has her most intense orgasms when she is kneeling upright, knees apart and the vibrator jammed against her clitoris with one hand, sometimes the other hand working on a nipple as well. When she's just about to cum she starts thrusting her hips backwards and forwards and usually has to contain herself not to scream. When we figured this position out we had some fun seeing what else we could do, one of the better experiments was her sitting on my face with my tongue licking her pussy.
However, she has the best orgasms in this position like this: She's on her knees with the vibrator settled against her clit. I'm lying on my back across in front of her, with my elbow on the bed between her knees, and my fingers cupping her arse and my thumb jammed up into her pussy. In this position, she can really push herself down onto my thumb (as my elbow is braced against the bed), and I thrust my thumb in and out and swirl it around inside her pussy to help push her over the edge. It's huge fun to watch and feel: she almost collapses when she cums. I'm usually jerking myself off with my other hand to provide her with extra entertainment.
It's only recently that I've realized that this technique does much the same thing as a Sybian, but at a fraction of the cost!