Drupal and Wordpress and just about any content management system will already have a web interface for creating posts of all sorts.
If you want local client application installed on your computer that can create posts and publish them to your site, try Windows Live Writer. I've used it with Wordpress and it actually works pretty well so long as you don't care about the silly markup Microsoft uses to keep things looking the way they want to.
If, however, you want recommendations regarding which of these programs to use for your website: 1) that's a bit out of scope for this site, and 2) you can't really install one of these systems without getting the whole package. There is not a way to install only part of Wordpress or part of Drupal. Of the two, I'd recommend Wordpress if all you want to do is create posts like a blog or news site.