I own a domain containing a trademarked word. I don't want to get into trouble with the trademark owner so my plan is to use the domain to display information (wiki-style) about the service the trademark owner provides. My question is whether I can display ads on this website to make money. For example, let's say I own Google.org (Google being a trademark). On this domain I would write about the real Google (history, business etc.) Can I get into trouble for having ads on this page including ones that promote other search engines (Yahoo, Bing, etc.).
To your actual question, sure you can display ads wherever you want; it's your site.
If you have a domain that includes a trademarked term, then go ahead and use it to talk about the product/service/whatever that trademark is attached to or possibly competitors(eg. in the ads), you need to get hold of a trademark attorney, and work out with them how, if at all, you can do that without basically asking to have the domain seized by the trademark owner. There are a few previous questions about this floating around if you do a little digging.
You probably don't want to use a trademarked name in your domain name regardless of how you plan to use it unless you have the explicit consent of the trademark holder. Some companies are fairly generous in granting this consent while others can be quite nasty about even perceived and questionable trademark violations (example, ask anyone who has tried to use 'bay' or 'monster' in a domain name). If you don't seek consent, then you'll have your site on the edge of destruction all them time. That's not where you want to be if you want to have a long term web property that you spend time and money developing.
Should you get consent, then how you conduct your advertising will depend on the conditions of that consent. For example, one popular forum I know of uses the trademark name in their domain with the permission of the trademark owner. They show Adsense ads that frequently display competing products and the trademark owner doesn't seem to have a problem with it. Another similar forum in a different niche is only allowed to show ads from the trademark owner and their authorized dealers.