This happened some time ago, when I was a student. I was a member of the climbing club, and we had our annual dinner at an inn up in the hills some way away. Those of us too poor to pay for a bedroom all crashed out on the floor of a function room, some more drunk than others. I suppose there was about 20 of us, 50:50 men:women, some married, some playing the field, some unattached.
I laid my sleeping bag in the middle, and what with the alcohol and the lateness I was dead to the world in 4 seconds flat. I awoke at some time in the night; it was pitch black and I lay listening to the small sounds of breathing around me, wondering if I would have a headache later on. I put my arms behind my head and stretched - the floor was none too soft for sleeping on. My hand encountered another hand. I made to pull away but the other hand caught at my fingers. It seemed to be a female hand, as far as I could tell, but I hadn't a clue who it belonged to. I tried to remember who had pitched their bag behind me, but with no success.
The cool fingers of the mystery woman explored my hand and wrist, then I felt her other hand touching me. She pulled slightly, and I got the message and wriggled up out a little so that our hands could slide down each other's arms. It was quite arousing and I had a sudden worry that it would turn out that She was another man. However that didn't stop me moving slowly across the floor, as (s)he did the same. Presumably (s)he could tell from the hairs on my arms that I was male. I paid more attention to what my fingertips were telling me and reassured myself that (s)he had extremely smooth and feminine arms for a man.
We touched each others faces and gently explored. Her fingers were incredibly gentle yet bold. As she reached my lips I took hold of her fingers and licked them, feeling her doing the same to mine. Her nails were short and rough; well, in a climber that is no indication of gender.
We were now lying head to head with our arms parallel, and I felt her shuffle further towards me. Her wandering hands continue to work their way down my neck and chest, and I followed her lead, trembling at what I might find. I breathed a silent prayer as I touched soft yielding mounds, warm from the confines of her sleeping bag. I sought out the nipples, bolder now, and massaged them softly. They grew hard slowly, and my cock, already swelling with the excitement, followed suit.
Suddenly I felt her head bump against mine. We twisted and began to feel each other's faces with our mouths, working down until our searching lips met. It was unusually erotic to kiss upside down. Actually it was not so much a kiss, more of a tongue fight. If I had been unsure before, now it was plainly obvious that the woman, whoever she was, was feeling extremely horny.
Our hands, which had been concentrating on the other's nipples, now resumed their journey downwards, while we continued to tongue each other and swap saliva. I could just about reach beyond her stomach to the top of her pubic bush, while she went straight for the tip of my erect cock and held it firmly.
I was desperate to go further and she must have been too, for she broke off our kiss and started to crawl onwards. I helped by wriggling upwards underneath her. She licked her way down onto my chest and took my hard nipples gently in her teeth. I felt her soft breasts dangling over my face and sucked on them gratefully, circling the nipples with my tongue, feeling the aureoles tighten and pucker. But there were more insistent needs to satisfy. We continued to voyage down each others' bodies - by now I was stroking her back, enjoying the play of muscles as she moved over me, and she dipped her stomach to caress my face. I managed to thrust my tongue into her navel as it went past, but then she had achieved her goal and I felt the tip of my cock engulfed in a hot wet cavern. Her teeth gently caught at the shaft - I nearly came on the spot.