This is something that happened about 12 years ago, when I was 20.
Some of the members of a sports club that I belonged to were having a social evening at the home of one of the members. The hostess was someone who I'd first met when I joined the club about a year earlier - at the time she was 41 years old, a divorcee. She wasn't exactly beautiful, but she definitely wasn't ugly either, and as I got to know her over the last few months we got on really well - to the point where we'd discreetly flirt with each other (only in fun) and make all sorts of subtle sexual innuendos.
As the social evening wore on we spent quite some time talking to each other. We'd both had a few drinks (but not so many that we were blind drunk - we both still knew exactly what we were doing ;-)), our inhibitions had partly melted away, and there was no mistaking the fact that she was coming on to me.
Neither of us wanted to make any sort of obvious move towards the other, but towards the end of the evening as the house became more sparsely populated, we slipped away to a room at the back of the ground floor, next to the kitchen, where it was quiet. Neither of us said anything, but we both knew what we were doing! We sat on the floor in front of the couch, and I began to run my hands over her body (she wasn't very tall, and not exactly slim, but she had some nice curves). She closed her eyes and started to moan quietly in appreciation - so I thought 'what the hell, I might as well have a little fun' and I began to rub her breasts through her blouse. Immediately I could feel that her nipples were extremely hard, and I guess that confirmation that she was enjoying this as much as I was spurred me on.
I unbuttoned her blouse, took it off, removed her bra (she was grinning from ear to ear by this point!) and began to stroke her now-naked breasts. I guess she got so excited that she just couldn't hold back any longer - she reached down into my lap and began to unfasten my trousers. I leaned back slightly to make it easier for her, and in just a few seconds she had my trousers unfastened, the waistband of my boxer shorts pulled down a little, and my cock (which was, as I'm sure you've worked out, rock-hard by now) in her hand. Wow! I couldn't believe it - here I was, with a woman old enough to be my mother, rubbing her tits and her wanking me off!
I guess this got her really horny, because she leaned towards me and simply said 'Rub my pussy!' I guess I shouldn't have been surprised, but I couldn't help thinking what a weird thing this was for her to be saying to someone a little less than half her age! But believe me, the surprise soon wore off, and she leaned back, lifted her legs up and I frantically pulled off her panties from under her skirt. Jeez! She had one of the most beautiful pussies I'd ever seen ... her hair neatly trimmed into a sort of triangle shape, her labia sticking out invitingly, I could just about see the tip of her clit poking out a tiny bit at the top, and of course she was so wet her pussy was glistening!
I didn't need asking again - we sat on the floor facing each other, her with her fist wrapped around my cock moving all the way from the base to right over the head and back again, me with two of my fingers gliding repeatedly up and down across her twat. After a couple of minutes of this, I just couldn't hold back any longer. 'I'm going to cum!' I warned her, just before shooting two or three ropes of sticky cum up onto her chest and stomach, followed by a few more dribbles which ran down over her still-pumping hand. As soon as I'd composed myself again, I quickly resumed my rubbing of her pussy and almost straight away she threw her head back and moaned loudly as she orgasmed.
I lay back onto the floor, exhausted, and she turned around to lay next to me. I couldn't believe we'd done that, with a few people still hanging around in the main room a couple of doors down the hallway.
Of course, once is never enough for some people - and lo and behold, a few moments later I felt her hand on my cock once again!!! It only took a few minutes of her stroking it up and down and fondling my balls for me to get hard again - she'd obviously done this many times before, 'cause this was one of the best hand-jobs I'd ever had!
Then the unthinkable happened ... the door to the room clicked open. We both froze, unable to believe that we were about to get caught out! But then it got worse - the person who walked in was the hostess's elder daughter (18 at the time - the younger 15 year old was out with friends). she just froze in the doorway, unable to believe what she was seeing - her mum wanking one of her friends (we weren't exactly great pals, but the daughter and I knew each other quite well). Of course, my face had gone the colour of a Stop signal, and I was trying to find some words to bluff my way out of the situation. But before I could say anything she came into the room, shut the door again, sat down on the couch and simply said, 'Don't mind me, you two carry on!!!'
Now I can only assume that she and her mother had a very open and relaxed relationship when it came to masturbation, because once she'd gotten over the initial shock she didn't really seem that fazed by the whole thing. I was a little reluctant to carry on at first, but the feeling of our wonderful hostess resuming her skillful stroking soon put paid to any ideas of making an exit! I'd partly lost my erection (what a surprise!) but our hostess's handiwork soon had me rock-hard once again. She was kneeling at my side, expertly working my dick and balls with two hands by now. Every now and then I'd glance across at the couch where the daughter was sitting, just to convince myself that this was actually happening to me, and each time I looked she was watching very intently. Of course, her fingers started to make their way to between her legs, and after a few minutes her skirt was up and her hand was inside her panties, very visibly rubbing away at her pussy while she watched her mum jerk me off. Now this was just too much, and without taking my eyes off her I had another belting orgasm. Having cum once about a quarter of an hour ago I didn't expect to shoot much this time, but I guess the extra visual stimulation had an amazing effect, 'cause I shot a single huge jet of cum over my shoulder (I was lying down) and all over the carpet. Another three or four spurts trickled out onto my stomach and the older woman's hand.
By now I didn't really know what to say, so I cleaned up as quickly as I could, made my excuses and left the two of them in the room while I went back to the front of the house where the last few guests were still milling about. I can only imagine what went on in that room after I left them (it's been something I've tried to imagine over and over again while masturbating!) But all I know is that when I left the party about 15 minutes later they were still in there!