We've been married for about a year. Lately, my husband has been talking about how much it turns him on to think of me having sex with another man. He's brought up the idea of a threesome, or just watching me with another. I have to admit, I'm a little turned on by the idea. Is it normal?

If you both are mature and really know it is something you would enjoy then be careful and plan, plan, plan. We would suggest that there needs to be trust and a good friendly relationship with the gentleman before you take the step. Someone you both enjoy socializing with enough that sex is not the focal point of the relationship.
Get rid of her she will go on having sex with others. I don't me to tell you how to live, just get rid of her