I've created a five-line Oddmuse module to display Google Adsense. I called her adsense.pl.
All it does is placing a piece of Javascript on the top of each page when the user is browsing (but not when editing a page, when using the administration screens et cetera).
To use, take the following steps:
- Login to your Adsense account, and copy the JavaScript code that's generated
- Create a new page called 'adsense' and paste the JavaScript code
- Lock the page if necessary; this piece of JavaScript will be added on top of every page on your Wiki
- Download the adsense.pl module and upload it into your modules directory
- Reload your home page, and voilà, your ad is shown! You might want to add a <div> or a <p align="center"> around your ad code.
There is a TODO list for this module, some of which I've already implemented.