Comment Contest allows you to manage contests on your website. This plug-in draws all comments in a specific post and show you the winners.
Shared Whiteboard is a WordPress plugin that makes it easy to add interactive whiteboards to your posts and pages.
Randomly select a winner or winners from the comments of a giveaway post.
Lets commenters add a drawing or doodle on a picture from a given post.
idraw allows you to create beautiful diagrams and insert them into your posts or pages directly.
The Gliffy plugin allows you to create diagrams and insert them into your posts or pages. Draw all kinds of diagrams: flowcharts, UI mockups, UML, etc
This plugin allows your visitors to draw an image as extra comment.
WordDraw enables you and your visitors to draw comments.
The Cacoo plugin for WordPress allows you to create diagrams and insert them into your posts.