This story is entirely true, with a few minor details modified to protect the guilty and to move the story along. It took place a little less than five years ago now, in the fall of 2001, when I was a junior in college.
The sorority girl in question (her name was June) had been a friend of mine since freshman year, but we never had any romantic connections. Both of us were dating other people, so while we were fairly close there was always that knowledge that we needed to maintain a certain distance. Still, there was definitely some sexual tension between us through those first two years. My girlfriend at the time lived in another state, and June's boyfriend was a very stable, nice guy, but just not at all into sex.
Over the years she would come hang out in my room quite often and we would chat about life, classes, etc. Sometimes the conversation would turn a bit toward sex, and she would complain about how non-existent her sex life was (and I how infrequent mine was). I could tell from her voice and how she sat and how her nipples would start to poke through her top that she wanted to take it a step further (and my cock was certainly telling me to...), but neither of us dared to cheat at the time, so we always stayed one step back from the brink.
The summer before our junior year, though, both of us broke up with our significant others. My girlfriend and I finally came to the realization that we were together more for the sex than anything else, and that while the sex was great it wasn't enough to keep us together considering we lived three hours apart... June came to the opposite realization - she still loved her boyfriend quite a bit, but just couldn't deal with having no sex life. She cheated on him, then finally just broke up with him. Starting junior year, then, we were both single, both horny, and finally both on the market at the same time
Things finally came to a head a month or so after classes started in the fall. June's sorority was having a hay ride, but June had no date. When she had signed up for the ride a few weeks earlier she was still dating her old boyfriend. In the time since they had finally, irreconcilably broken up (he finally found out she was cheating on him), but she had already paid for his place on the ride. Knowing that I was single too and looking for something to do over the weekend, she invited me to come along.
The hayride itself started out with your typical college debauchery. Everyone had "water bottles" full of various cheap liquors. Some local farmer showed up at the sorority house around 9pm with a tractor pulling a wagon full of hay, and we all loaded on. The plan was for him to drive us back to his farm, where there was a clearing in the woods with a bonfire already started and set up where we could party for a few hours, and then get a ride back to the sorority house. Good clean fun, no chance for anyone to get in trouble for DUI, no noise complaints, etc. All in all a nice arrangement.