Ok, now I remembered what I was going to write.
Before I describe this one, be forewarned, this is only useful if you like the deep slow burn kind of sex, not the jackhammer pounding.
While doing the normal missionary, go deep enough so your glans is in contact with her posterior fornix. Now concentrate on what's going on above her torso...
**SLAP** PAY ATTENTION... ABOVE HER TORSO
Kiss her up and down her neck, be gentle with her, caress her breasts, let your hands roam, but above all leave your cock motionless inside her, filling her up, almost painfully, but just a not-so-gentle reminder that you are firmly planted inside her.
Involuntarily, she will start squeezing little squeezes to compensate for the motionlessness. Now prop yourself up, gaze at her lovingly and ever so slowly pull yourself out. Because of the vacuum seal formed from the squeezes, the depth, and the contact, both of you will feel a little tug on your cockhead, then a pop. You're actually slightly pulling the back of her vagina out with your cock, and the pop is this vacuum being relieved.
This is where length counts...
She'll feel your absence back there, she's hungry, she'll want to pull you back into her again. This time (since you were propped up) you lay back down on her to kiss. As you're lowering your face downward to kiss her, push in. But don't push in like before, push in deeper. Much deeper. She's needing to be filled, moreso than before because now she feels the void deep insider her.
Don't just push in though, push in and ride high so your cock is using her entrance as a fulcrum to push you deep and downward away from her uterus and cervix. I've noticed my wife's vagina more capable of being stretched downward (towards her spine) more easily than upward (towards her bellybutton).
She'll either cum or ask you to stop what your doing. If she cums, high five. If she tells you to stop whatever the fuck you're doing, blame me and report back here for instructions on the best deals for jewelry and flowers.