How does the Bible define sex within marriage?

I've read a number of Christian sex books. I can't remember which one, but it said oral was wrong, as were toys. Another said anal was wrong.

Personally, I don't see anything wrong with anything within marriage if both parties agree, and I've heard sermons stating this.

It's not like you'll find much about it in the Bible saying that certain sexual practices between a husband and wife are okay or not.