Social phobic or not, all men have a competetive nature. Seeing other men getting the girls, leading the pack, going to parties and getting all the attention is probably getting under your skin because of this. I went through the same exact thing in school as a kid, I'd see other guys living it up and I'd realize that by my extreme shyness (didn't know what social phobia was back then) I would never be able to be as cool as them. So what did I do...?
First I would convince myself that theirs was not the life for me, I'd try vainly to dispute all the benefits of being the football team captain or the chick-magnet party-goer dude and tell myself their lives actually sucked. I'd watch them in the halls laughing and acting all super happy and I'd tell myself "they're so fake" or "they're probably going to end up getting arrested for throwing outrageous parties with alcohol and drugs." I'd tell myself anything to make myself feel better when in reality I wished for a taste of their life, just a little bit of attention from the cool kids.
One thing led to another and it became a habit, every day I'd see one of them I'd go straight to the dark thoughts instantly, and before long I was doing what you're doing--imagining ill things upon them, like "I hope he crashes and dies when he's driving home today so his big clique of popular people will be saddened and cry for months on end." It's just a coping mechanism like the others in this thread are saying, it's not illegal, it's not going to turn you into a psychopath.
One thing that helped me out in high school was my skill at soccer. I was on the soccer team, so I always knew that maybe the cool kid can get all the chicks but I could always smoke him at soccer. Find something you're good at, even if it's something obscure like art or poetry or something and focus on mastering it. I guarantee you there are chicks who dig artsy dudes, and it will help take your mind off taking joy from other peoples' misfortunes.
Try going to one of the parties, but tell the person inviting you that you can only stay for an hour or so. Just stroll in there and say hi to a few people and then bounce. The fact that you're making an appearance at the party (however brief) will get you noticed and people will start wanting to get to know you. Don't worry about sex, the kids who are rushing to bang every female they see are the insecure ones, who have to find out if they're pornstar material right away in case they're gonna die the next day.
