In a previous post, I mentioned a GreaseMonkey script which pushes starred items from Google Reader into Delicious. Here's a demo, and here's the small script: http://userscripts.org/scripts/show/49405.
The tricky part was extracting the right info from the Reader page. The Delicious API makes it easy to post new bookmarks. It would be straightforward to mod the script to post Reader stars to other apps with decent APIs -- perhaps Twitter (api), FriendFeed (api), Facebook (api), what have you.
Update: found really well done existing Google Reader To Twitter script: http://userscripts.org/script/show/10169
Update II: also check out JetPack, a just-released Mozilla project that promises to do what GM does, only slicker and easier: http://labs.mozilla.com/2009/05/introducing-jetpack-call-for-participation/. Looks promising.