A huge fantasy of mine...

Has anyone ever just watched another couple have sex (friends or otherwise) and tossed one off?

in real life? no but i would loooooooooooooove to

Not in real life. But, one time on Skype a guy had a smartphone and gave me a great view of him fucking his wife from behind while I jacked off.

Once. We chatted online for a week or so prior then one evening they got a hotel room and left the curtains and door open so I could watch for a minute to feel comfortable. After a few I went in an sat down next to them. Never really said much other than hi. She was sucking his cock so I finally pulled mine out. Over ther next 20 min they fucked and I jerked. I said I was getting close she he rolled her onto her back and started fucking her and told me to cum on her face. I blew a nice load all over her face as he fucked her. She said thanks I wiped off and left. Pretty damn good time.

Again not in real life but once found a couple and they got on cam and she sucked him while I jerked on cam then she got a toy started using it on cam and she moaned my name and I exploded!

One evening about 3 months after Bibi and I were married, we invited my secretary Hedy and her husband over for dinner. My office was a very non-formal, usually just my secretary and some of my workers dropping by every so often. Our conversations very often were down right XXX rated. She knew damn well that I would have to screw the hell out of her, and her husband had the feeling about Bibi. That night they came over, we planned to play some poker and it quickly turned to strip-poker. We agreed ahead of time that the last person with any clothes on, could have their way with whoever they wanted. I was left with my shorts still on when Hedy lost her panties.
I said "OK I won, Hedy come over here and spread your legs. As I just about to plow into Hedy"s cunt, her hubby dropped his shorts and helped Bibi take her bra and knickers off. Needless to say, a good time was had by all.

No, but always wanted to.
Closest I have been to that kind of situation was my girlfriend and I being in the back seat of a car with my bands guitar player up front and his girlfriend driving.
Was not expecting her to pull off onto a side road and she got on top of him riding his cock in the front seat. Watching them got me horny and I asked my girlfriend if she wanted to fuck too, but she wasn't comfortable with doing it there, so I asked if she would suck my dick and she kind of reluctantly agreed, but this is the girlfriend I had who hated that I jacked off at all, even when she wasn't there and hated that I looked at porn magazines and videos while I did it, hated sucking dick, but finally started doing that after I was able to get past her trying to stop me from eating her pussy, but once I was able to finally get my tongue in there she stopped fighting it and let me do it and finally agreed to trying sucking my dick, but she was never enthusiastic about it and never volunteered to do it.
Anyway, in the car I was sitting up in the back seat while she laid across the seat with her head in my lap sucking my dick. I was going back and forth between watching her suck me off and watching my friends girlfriend riding his cock in the front seat with her awesome tits hanging out. She was hot!
My girlfriend stopped sucking after a few minutes with a mad look on her face and being upset the rest of the night.
She told me later that she hated it enough when I jack off to other women in porn or to the thought of other girls I know but that it upset her more that I was looking at another girl in person, especially a friend of ours and she knew I was thinking about her body and wanting to fuck her and would have been bad if I had been jacking off while watching them fuck and jacking off while thinking about fucking his girlfriend, but she was even more upset that I asked her to suck my dick while I watched them and thinking of fucking that girl more than I was about her while she was sucking my dick when I knew she hates doing that. She felt like she was rewarding me for pretending I was fucking my friends girlfriend.
She also did not like that the other girl was watching us and looking at my cock.
Yeah, so that was a huge buzzkill. Had I been without her I would have just jacked off watching them, but if I had not had her with me I don't think they would have stopped to fuck. Most of my girlfriends would have sucked me off and/or fucked me in that back seat with no problem and would have been getting just as turned on watching them as I did.

Only other way I have come close to this was hearing other people fuck in another room of the house, another apartment or especially a hotel room and jacked off imagining what was happening in there and wishing I could watch.

I shared a house with a couple of guys I worked with. One of them moved his girlfriend in. They would fuck every second day pretty much. One night I was downstairs alone watching TV when they started fucking. She was moaning and the bed was squeaking like crazy. I went into the room directly under theirs, got my cock out and wanked. I noticed her washing was in the room and I took a pair of her black panties, hung them on my cock and wanked off. I came when I reckoned her boyfriend was cumming. I wish that girl know she had two cocks hard in that house, one fucking her and one wanking for her as she had a cock in her cunt, her black lace panties on the other cock. If she knew I had my cock out within six feet of her while she was getting fucked, she would go mental.

Hot story! Really miss shared houses and hearing my housemates fuck.

At uni one of my housemates was a bit of a loner and stayed in his room all the time. My room was adjoining his and I used to have my gf over a lot. Loved the idea that he could hear my gf moan and be wanking off to her as she got fucked.

Yes,
I have stroked it watching a couple fuck in a porn theater and when I help guys fuck their wives. Hubby is jacking while he watches me fuck her and then I tag out, he tags in and I jack while I watch him fuck her.

House party. Drunk crash in bed. Wake at dawn to naked couple in the bed next to me getting groovy. big tits. Hard cock plunging into a pretty beaver. Best time ever.

my wife and I went to a guys house and she modeled lingerie and sucked me off while he relaxed and masturbated. it was great fun

several times in porn theaters, but never with anyone I knew

Many times.