moisture problem inside

I live in a town that, for some reason, has a high number of homes with mold problems. My home was treated for mold a year and a half ago, before we moved in. Lately, when I come in from being out, my house smells musty... as if there is a moisture problem, and a mold problem again.

I set up a dehumidifier in the room with the biggest problem, but I was wondering if anyone had any other advice on things I could do to fight back the moisture.

Thanks