Naked Twitter for Safari extension by Jacob Bijani cuts the display down to the minimum when browsing Twitter.

Features:
No sidebar at all! The only links I use are replaced with icons at the top.
No hover cards, hover tips or lists.
Adjusted some inconsistent padding here and there.

Jacob Bijani has also made a Naked YouTube extension for Safari

Download at: http://jacobbijani.com

Related posts:

1. Using Twitter to crowd-source the world
2. New Micro Blogging Web Site Rivals Twitter and Facebook
3. New Twitter how-to course explains how to build a massive and responsive Twitter following