Chrome/Firefox (Greasemonkey): If you're not a fan of the Google+ integration in Google Reader or you simply wish you could still use the old sharing system, ReaderSharer is an extension that restores those functions.
The extension brings back the Shared Items, share button, and Trends options from the old version of Reader, while still retaining all the new options like +1's. Currently the Firefox implementation is through a Greasemonkey userscript, but in Chrome it's a standard extension. There are conflicts with Adblock at the moment, so if you're using it, you'll need to disable it for the Reader page to get it to work.
ReaderSharer | Chrome Web Store via Addictive Tips