This follows the same principles as selling your blog theme but applies to any custom plugins that you've developed. Like with selling blog themes, there's an abundance of custom plugin marketplaces, for example, Code Canyon, WP Plugins and Extendd.

Advantages: This is another quick method of making money if you've already developed the plugins for your own blog. All it's a case of is listing them on plugin marketplaces and watching the money come in (assuming they add genuine value).

Disadvantages: One obvious stumbling block for this method is actually having the plugins in the first place. Developing the plugins from scratch can be incredibly time consuming, so unless you've got the resources to develop the plugins, this might not be an option for you.