One way that I notice alot of E/N sites such as myself are making their money is by selling links in a noticeboard at the very top of their site. Basically... it would be a module that randomly chooses 4 or 5 links (that expire) for a database of them upon every refresh of the page. And then there would be a counter so that people can see how much traffic they would be getting:

Example:
Zfilter
It's at the very top of the page.

I have no programming skill.. so I'm not sure hard it would be to integrate into xoops.

That's a very good concept to make some coin.

Yeah.. it's a really compact way to sell ad space on your site without seeming to overwhelming like some banner ads are.