Go for a classic costume, like a pirate costume, or better yet, put together a Jack Sparrow costume from Pirates of the Caribbean: Dead Man's Chest and go out as a movie character rather than just a plain old pirate. These few ideas are but an inkling of what is out there for men who are willing to take a little time to make this Halloween a memorable one.
The internet (that's what you are currently looking at) can be useful for all means of information, like where to buy Halloween costumes or places that have ideas for costumes. If you are looking to make a spider man alien costume, you won't find your costume on the web, but if you are looking for a broader topic, say, a sexy man costume, you might have more luck. And if you are really lost in it, use a search engine; and don't be afraid of nominal phrases (i.e. 3 costume man spider venom) that seem to make no sense, but will garner the searches you want.
Choices Choices Choices
What it all comes down to is really whether or not you want to make a replica spider man costume or will be ok in the spidey pajamas and mask. There is a difference between a man who will dress up for Halloween or one who will shrug the whole idea off. You can tell when a guy went out and bought his man renaissance costume that looks like it was stolen from a movie set and the guy who is wearing the tin man costume that actually is a stolen garbage can. Not to say one or the other is in the right, they are both good Halloween costumes for different reasons. The same is true for the person who will build their own black spider man costume from the upcoming Spiderman movie and the guy who goes out and buys the x man costume consisting of nothing more than a 12 dollar jumpsuit and mask. They will both get you into a costume party, but one actually has thought and effort that went into the costume, so it ends up turning out better. It doesn't have to cost more, it just has to have a bit of effort. It lends your costume credibility when it looks like an authentic spider man costume as opposed to a red and blue jumpsuit coupled with a ski mask and you tell everyone you are in your adult spider man costume when you look like a child whose parent's forgot it was Halloween. It is just more fun to go all out. So this Halloween, rather than going out in that old iron man costume or that burning man costume from back in your college days, take a little time and look for a good sexy man costume or a real spider man costume.
P.S. If you are looking for the black spider man costume, good luck. The movie doesn't even come out for another year.