The threat of his being so not into it is very real for a lot of married couples. Eventually you will have to decide to tell him, I suggest you do that before getting involved in the poly community as you could find someone interesting and fall into a situation that makes you lose your integrity.
Integrity is very important, as is respect, honesty and empathy. You don't sound like you have built on these foundations yet and that will lead you to unwanted trouble I think.
I suggest you gets some book (check the book reccomendstions sticky) and begin reading them. He could notice this and ask what they are. You could talk about this site too or other things you find on line. That could be a segway into asking him what he thinks..if he says its bullshit, that is where you get to say, "actually, it makes sense to me and here's why."
Starting with questions is sometimes easier than coming out...
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