This really has nothing to do with mapping, but I thought that maybe someone around here might lend a little insight.

If I wanted to make an adventure (or six), compile it into a .pdf and distribute it for free, what would I have to do to make sure that I stay within the law?

I'm specifically talking about 4e here, but really any setting and/or rules system should apply. I understand that posting complete stat blocks of existing published monsters and characters would probably be a violation of IP laws and such, but I should just be able to reference page numbers and tell you what creatures are in the encounter, shouldn't I? And creatures of my own design, providing they're not specifically listed as intellectual property (beholders, carrion crawlers, etc.), should be allowed full statistics, no?

Anyone have any advise on this, or know where to turn for further information?

Thanks in advance.