you've received some pretty good advice from most of the other posters already. if your son is gay, you basically need to support him and love him for who he is. definitely do *not* send him to a "fix it" camp. your wife needs the counseling, not your son.
however... there's something else to consider (something I haven't seen from others here yet). your son might *not* be gay. wtf I hear you (and others exclaim?). just because he was making out with a guy does not necessarily mean he's gay, or even bi. he might just be experimenting. he might have just been horny as heck and figured "what the heck, let's do it." i'm not saying (at all), that he is *not* gay. he very well might be.
what you should do is talk to your son about sex in general, and sexuality. i have no idea what your talks on the subject are in the past. how much (if at all) have you talked with him about the subject? if never... well... now's a pretty darned good time to get started! at the very least you owe it to him to discuss safe sex. that will probably be the *least uncomfortable* topic to start with. regardless of whether he's gay or straight... you have to talk about STDs, AIDs and, definitely, *condoms*. now... getting to talk about sexuality with your son is going to be more uncomfortable... and (as a father myself)... you might want to talk about your own sexuality. did you ever experiment?
of course, you've got to be really careful not to be judgmental at all, be 100% supportive and understanding. good luck to you... and... you also really need to talk to your wife... perhaps show her this thread!