Luke Gedeon

The default position for the menu in WordPress 2.7 is on the left, but since the scroll-bar is on the right, some people wanted the menu over there too. Plus a lot of blogs/websites have menus on the right so menu on the right seems to be a pretty popular option.
This plug-in moves WordPress admin menu to the right side of the screen.

Admin Menu on Right

Moves WordPress admin menu to the right side of the screen.

borantula

Most of the plugins and even standart WordPress tabs in the admin menu are not used very often. 
With this plugin you can make rarely used items in the admin menu invisible until you need them. 
You can just toggle them whenever you need them with Toggle Extra button in the left menu.

Clean WP Admin Menu

Still works!

You can make rarely used items in the admin menu hidden.

Admin Menu on Right vs Clean WP Admin Menu