Simple “write post” page?

I want to give access to my visitors the ability to write posts in the easiest way for them – when they go to the “write post” page I want to show them only the post title/text field, the categories list, the file upload field and “save” button 🙂

How can I do this? Is there a plugin for this(searched for this type of plugin but didnt found anything), or alrady build-in-wordpress-feature ?