Moode.org Info: Blocks
The link will take you to information about all blocks in Moodle. Blocks can be placed in a tab on the left side of the screen via the Dock icon – 
Instructor Block
A simple block to display the instructor’s profile. If there are multiple instructors assigned to a course, each will be displayed in the block.
Add Custom Information Using HTML Block
If you would like to include additional information in a block (such as general availability or communications response time) you can add an HTML block.
How to add a Twitter widget in your Moodle course
This requires logging into your Twitter account.