Have you seen the PSAs that Google push out when there are no relevant ads?
If Google cannot match ads to your site’s content you end up displaying non-paying Public Service Ads.
Eric Giguere points out a new service that is designed specifically to fill those gaps:
AlternateURL.com which introduces its benefits as:
Most online ad programs, including Google, will sometimes show default ads, or public service announcements (PSAs) when they have no paying ads to show. This can happen for many reasons, especially when their ad code crawls your pages.
AlternateURL lets you replace those ads with paying ads. You could be wasting a lot of adviews — and losing a lot of money — by not replacing AdSense PSA ads.
You can see what their ads look like here
From reading their terms and conditions and FAQ it seems that this is open to Irish users as well, so I’ll probably signup later today.
The only restriction that I can see is that they only payout via Paypal, but that wouldn’t bother me in the least.