There are plenty of popular user-generated content sites around these days. In order to start your own, you need to give your visitors a simple way to submit their images and content. User Submitted Posts for WordPress can help with that. It is a simple plugin that lets your readers submit posts and images on the front-end.
User Submitted Posts lets your visitors submit posts from anywhere on your site. They can include title, tags, category, URL, and other fields with their submission. The script comes with input validation and anti-spam measures. Webmasters can choose a redirection URL upon a successful submission.
User Submitted Posts allows use of WP’s text editor for post content. You can display the submission form anywhere using the appropriate template tag or shortcode. This is a free plugin.