This happened to me a few days ago and was awesome. First things first though. I'm 5'11' with dark brown hair and quite a thick 7 inch penis. I have been masturbating since I was 12 or 13.
One night I was on a chat room talking to a girl I know (who I'll call Emily) who like me is bisexual. We are pretty open about sex and even though she has a boyfriend, we masturbate together quite a lot on line.
Anyway, we made small talk for about 10 minutes then I turn on the web cam so she can see me. We carry on talking and soon that conversation turns to sex. After a while I start getting hard. Just to say before now she has never seen me naked and I've never seen her naked either. I suddenly ask Emily if she wants to see me 'down there' now that I have a web cam. She agrees and so I take off my shirt and then my jeans and boxers. I was fully erect now and sitting in front of the webcam completely naked!
We carry on talking about random stuff and before long she asks me if I wanted to deal with that now. I quickly agree and start slowly wanking off to her. After about 5 minutes she says that she is now masturbating in time to me. What a thrill. We talk about the sensations we are feeling while going at it. It wasn't long before I was telling her I was nearly done and about 10 strokes later my orgasm starts and I shoot off 5 ropes of hot cum.
Emily says she's nearly there and I encourage her by saying things like 'that's it baby cum for me'. this must have put her over the edge because a few seconds later she said 'omg that was intense!' we say our goodbyes to each other and go off-line.
I hope she gets a web cam soon so I can see her masturbating as well.