Recently, I signed up to be an Amazon.com Associate and I wanted use this so I could reference books on Amazon that I reviewed using their "buy now" button. In order to make this work in Community Server, I had to make a small change in the communityserver.config file for my site.
By default, there are only certain tags that Community Server 2.0 (CS2) will allow you to use within your posts. It turns out that the Amazon Associate program uses an iframe (as do other referral programs) to display their content on your page and this is one of the tags that CS2 does not allow. So I simply needed to add that tag to the below file "communityserver.config". The section below shows what you need to add to the html tag (there's more in that tag)
<CommunityServer><MarkUp><html>
... other tags ...
<iframe style="true" src="true" marginheight="true" marginwidth="true" frameborder="true" scrolling="true"/>
</html></MarkUp></CommunityServer>
You must set the attributes as well and enable them by setting their value to true. Also, once you upload this file change to your site, it may not take right away. So you may need to "touch" your web.config file (I just add a space somewhere in the file and save it) as that will reset the ASP.NET application and force it to "reload".
Perhaps there's more to it than this, but it's a good start.