I have wanted to display items marked as "shared" from my Google Reader on my blog for a while and today I finally sat down and wrote a plugin to do it. You can download the source at http://mike.crute.org/downloads/reader_shared.phps.
I wrote the plugin with the following two assumptions: you must have a copy of PHP with SimpleXML and you must have url_fopen set to true. I also do not do any error checking on the settings page so if you feed it bad settings its likely to bomb in a very un-graceful way.
To use it just drop the code in your wp-content/plugins directory and set the settings on the Options page. Then modify your template and add a call to readerShared(); wherever you would like to see the listing of your shared items.
The "I'm Reading" box on the right hand side of this blog is powered by this code.
Update (1/17/07): The Google Reader folks where nice enough to point out my little Wordpress plugin on their blog. If I get enough interest I would entertain maintaining and extending the plugin. If not, it still suits my needs.