WordPress allow guest users to write a post
I’ve been long searching for something that makes this possible, and while you certainly had options (four or five plugins exist for quite some time now), none of them worked as well as I hoped, plus, they always missed a couple of important features, at least for me. Well, that search has come to an end, meet Post From Site plugin.
In a nutshell, what you can accomplish with this plugin is to allow users to publish posts without having to register with all the standard options like default category, publish to a post or to a page and so on, decide whether you want to bring a form in a popup, or have it embed in your page. To top it all off, you can use the plugin through a widget, with a short code or with PHP code written directly to your template.
I’ve used it to create a Twitter like design. You allow anonymous users to publish, you set the default category in the back-end, you embed a form in your site and that’s it! You can have something like this that directly creates a post.
Is someone starts making problems you can enable Google’s Recaptcha, you can allow anonymous users to only create drafts which you have to approve and so on. All in all, this is the best option to allow guest users to write a post, in my humble opinion. Be sure to give it a try.