Helvetireader-safari-extension is a project mainly written in JavaScript, it's free.
Safari 5 Extension for Helvetireader skin for Google Reader
Safari 5 Extension for Helvetireader http://helvetireader.com
Go to Safari Preferences → Advanced → tick Show Develop menu in menu bar
In the menu bar go to Develop → Enable Extensions
Download Helvetireader.safariextz
http://github.com/downloads/ronny/helvetireader-safari-extension/Helvetireader.safariextz
Double click the .safariextz file to install in Safari 5 and follow the prompts
Helvetireader by Jon Hicks (http://www.hicksdesign.co.uk) with favicon override by MkFly.
Extension icon taken from Joshua Brewer's Flickr page.
I (ronny) simply repackaged it for Safari 5.
This extension comes with NO WARRANTY whatsoever. But feel free to log any issues in http://github.com/ronny/helvetireader-safari-extension/issues
Have fun! -- Ronny Haryanto