I know there are a lot of these stories already, but the more the marrier. I like reading about girlfriends who end up sleeping with another guy (or two) while he boyfriend watches (or joins). 
*edit* especially when she does stuff for the other guys that she wouldn't with her boyfriend (ie. swallow, anal)
*edit* especially when she does stuff for the other guys that she wouldn't with her boyfriend (ie. swallow, anal)