13th, 14th and 15th WAY

13. Marketplaces
Sitepoint is the online marketplace by excellence. Some websites and blogs, however, are trying to replicate that model on a smaller scale.
Depending on your niche, a market place that allows your visitors to buy, sell and trade products could work well. Over the time you could start charging a small fee for new product listings.
The problem with this method is that there are no standard software on the web, so you would need to hire a coder to get a marketplace integrated into your website.
You can see an example of a marketplaces being used on EasyWordpress and on Mashable.
14. Paid Surveys and Polls
There are services that will pay you money to run a small survey or poll on your website. The most popular one is called Vizu Answers.
Basically you need to sign up with them, and select the kind of polls that you want to run your site. Most of these services operate under a CPM model.
15. Selling or Renting Internal Pages
Million Dollar Wiki made this concept popular, but it was being used on the web for a long time around (check Pagerank10.co.uk for instance).
These websites sell for a single fee or rent for a recurring fee internal pages on their domain. Usually they have either high Pagerak or high traffic, so that people purchasing a page will be able to benefit in some way.
Implementing this method on a small blog would be difficult, but the concept is interesting and could be explored further.