I consider myself bi psychologically but mostly straight in practice. Unfortunately I have not had as many "bi mmf" experiences as I wanted to, although the good news is, my wife is up for one! I was in a long term MMF threesome relationship once but I was not attracted to the guy and never did anything with him - he'd usually fuck his gf while she sucked my cock and that was it.
Later on, I developed a gay crush on a friend of mine, and we fooled around a few times - got naked, made out, stroked cock but we'd usually do this drunk and pass out before we could get down to blowing each other and cumming and we'd wake up naked and confused.
Another time I had a MMF with my GF at the time and her roommate - mostly she would suck his dick while I was fucking her and she also sucked both of our dicks together, managing to fit both in her mouth at once while he and I made out. That was hot, and I loved making out with her and tasting his cock on her tongue.
Lastly, I had a MMFF foursome, which was very hot. The girls licked each others pussies and the other guy and myself stroked, made out and sucked each others dicks, then we jerked off and came on the girls. This was probably the best time, but I am still eager to try more. I'm also curious about topping a guy b/c wife is uptight about anal and I only get to do it on special occassions few and far between.
There's a site called
First Bi Threesome that has some pretty accurate information about this subject. I wish male bisexuality was more open and acceptable, then I would have had more to share.
Oh and btw, making out with a girl while you have a cock between your lips is the fucking BEST!