Twitdrang is a userscript that makes the timeline at twitter.com narrower. I use it and Fluid to make a smallish site-specific browser (SSB) dedicated to Twitter.
The timeline looks like this
Scrolling to the right reveals the sidebar with the other Twitter tools.
install.sh script copies the userscript from the working folder to the appropriate spot in
~/Library/Application Support/Fluid. The Twitter SSB I use this with is just called "Twitter." If you use a different name for your SSB, you'll have to change the destination folder name in