Most notable of these is Blogads, which advertises itself as a "network of influencial bloggers who accept advertising".

They state that the average blogger (weblog author, that is) makes $50/month selling Blogads, which isn't too bad at all.

But there are two issues here that you need to consider before you get too hyped up about this:

1. "influencial bloggers" seems to suggest that they don't just take any weblog author into their program, so you probably need a minimum amount of traffic or segment visibility to be approved. You can find out for yourself by signing up for Blogads. And if you have been rejected (or even if you're now running Blogads) please report here and let us know how you're doing.

2. More and more, the traffic to my own Weblogs, notably The Intuitive Life and Real Life Debt: The Weblog, is coming in the form of RSS feeds (Learn more about RSS), which cannot serve up the Blogads. So, while a blogger might have a total of, say, 500 daily readers, it might well be the case that 200 or more are just tapping into the RSS feed and using an RSS reader to keep up-to-date rather than a Web browser.

While Blogads says that revenue will increase as time passes, my suspicion is that revenue might actually decrease unless they can tackle the question of adversiting showing up within the RSS feed itself.

And it's worth noting that currently Google Adsense can only appear on Web pages too, but they are experimenting with Adsense within email messages (newsletters, not individual messages) and it wouldn't be much of a leap to have a slim, lightweight Adsense advert appear within an RSS feed too.

The flip side of this is that when magazines get too many advertisements, people stop reading them or insist that they be offered for free rather than via subscription, changing the entire economic model of the business. So perhaps the question isn't whether Adsense or Blogads can appear in the RSS feed, the question is: is someone creating an advertising network exclusively for the world of RSS and other content feed systems?

In the meantime, if you do have a weblog ("blog") that gets decent traffic and you're interested in revenue opportunities, don't constrain yourself to affiliate marketing programs: check out the different advertising networks too.

Oh! One more quick note: the Adsense terms of service prohibit other ad networks showing up on the same page:

"We do not permit AdWords ads to be published on web pages that also contain what could be considered competing ads. This would include all content-targeted ads as well as text-based ads. Text-based ads, for this situation, can be loosely defined as ads that mimic AdWords ads or appear to be associated with AdWords ads on your site. We do allow affiliate or limited-text links."