Firefox with Greasemonkey: Previously mentioned Stylish script Google Reader Absolutely Compact removes a lot of the Google Reader interface to get more on-screen, but for some it takes away too much. Google Reader Absolutely Customizable lets you choose what to hide.
After installing the Absolutely Customizable script, to access the options dialog (pictured above) go to Tools -> Greasemonkey -> User Script Commands -> Google Reader Absolutely Customizable Options. After choosing the options you want, click Save and the page will be refreshed with the new options in effect.
All the tweaks from Absolutely Compact are in Absolutely Customizable, plus the ability to resize large images in posts from Google Reader Image Resizer. Google Reader Absolutely Customizable is a free download, requires Greasemonkey and Firefox.
What's your favourite tweak for streamlining Google Reader? Let us know in the comments.
Google Reader Absolutely Customizable [Userscripts.org]