1. Ad networks
These are services like AdSense and Chitika but also smaller or more local ones like NuffNang (which operates out of Australia and Asia). They can probably fit in some of the other categories as well, as they use different models to deliver their ads.
This is where you sell space for an ad and get paid based upon how many times it loads. Usually you get paid per 1000 impressions of the ad. The rate varies a lot, depending upon topic. There are lots of very low, “remnant” ad networks out there that pay you a pittance per impression, but if you have a higher value niche you can get better money. I’ve been paid up to $40 per 1000 impressions.
3. Cost Per Acquisition (CPA)
These ads pay out only when someone takes some kind of action after clicking the ad. The action might be a sale but could also be them signing up for a service, leaving an email address, etc.
4. Cost Per Click (CPC)
This is what AdSense used to be: every time someone clicked your ad, you’d get a certain amount. Now AdSense do a combination of CPC and CPM ads—they mix them in.
This is what I do on ProBlogger. I sell ad spots on a month-by-month basis to sponsors for a fixed amount per month.
6. Text links
When you sell a text link on your site, the person buying the link is usually doing it for search engine ranking purposes. As a result, Google frowns on these and you could be risking your own search rankings by doing it. I don’t do this, as I see it as a little too risky, but some bloggers still do. Proceed with caution.
7. Pay per post
Also known as sponsored posts (advertorials), this is where you’re paid to review a product or to promote it in a post. Bloggers have varied ethical stances on this. Generally these days you are required to disclose that you’re being paid for the post.
8. Job board/classifieds
If you operate in a niche where people are buying and selling products or there are jobs that people want to advertise this can be a nice source of income. You need to be able to attract both advertisers and those they want to see the ads to make it work, though—so you need traffic and profile.
9. Newsletter advertising
This is a growing area for me. Some advertisers love to have their brand included in emails that you send to readers. We find bundling some onsite sponsorship banner ads with inclusions in our newsletter is a good way to sell space to advertisers.
Some ad networks (like AdSense) have ways of doing this but you can also sell sponsorships in your RSS feed directly. We use a WordPress plugin called RSS Footer to add an advertisement in the RSS feed of ProBlogger.
Here are a few more ideas that I should add to the mindmap…
Ad networks like Kontera offer these, and I think Chitika and a few others do, too. They are ads that appear in your posts, turning certain keywords into little ads (they usually change the color of the word and/or underline it to make it look like a link). When someone hovers over the word a little ad pops up with a description of a product that they can buy. Some bloggers find these ads convert well, but others find them intrusive.
12. Video advertising
If you publish videos, you might be interested in Youtube’s integration with AdSense, which allows you to earn money from ads that appear in your videos.
13. Image ads
Yesterday +Scott Fitzgerald alerted me to ImageSpace Media, who have a system that adds advertisements into your images. These are similar to the ads you might see in Youtube videos that pop up and that can be minimized.