I'm not a regular twitter user, and it's too annoying to manually create the rss feed url for the twitter feeds I do want to follow in Google Reader. Their bookmarklet doesn't get the job done, but this one (twitter-specific) does. Just bookmark the "compiled" version.

twitter-to-google-reader-compiled.js

javascript:(function(){var%20canonical%3D%22%22%3Bvar%20links%3Ddocument.getElementsByTagName(%22link%22)%3Bfor(var%20i%3D0%3Bi%3Clinks.length%3Bi%2B%2B)%7Bif(links%5Bi%5D.getAttribute(%22rel%22)%3D%3D%3D%22canonical%22)%7Bvoid(canonical%3Dlinks%5Bi%5D.getAttribute(%22href%22))%7D%7Dif(canonical)%7Bvar%20feed%3D%22https%3A%2F%2Fapi.twitter.com%2F1%2Fstatuses%2Fuser_timeline.rss%3Fscreen_name%3D%22%2Bcanonical.substr(canonical.lastIndexOf('%2F')%2B1)%3Blocation%3D'http%3A%2F%2Fwww.google.com%2Freader%2Fview%2Ffeed%2F'%2BencodeURIComponent(feed)%7D})();

twitter-to-google-reader.js

// Use this tool to keep the full-form js maintainable:
// http://jsbeautifier.org/
//
// and this tool to turn it into a bookmarklet:
// (enable "shrink vars" and "into bookmarklet")
// http://zenoplex.jp/tools/javascript_packer.html
//
// Based on original google reader bookmarklet.
//
// Get canonical URL for easy extraction of twitter handle
// thanks to http://stackoverflow.com/q/5980682/265522
var canonical = "";
var links = document.getElementsByTagName("link");
for (var i = 0; i < links.length; i++) {
    if (links[i].getAttribute("rel") === "canonical") {
        void(canonical = links[i].getAttribute("href"));
    }
}
if (canonical) {
    // Grab user name from canonical url like https://twitter.com/luanews
    // thanks to http://stackoverflow.com/q/4758103/265522
    // then build the feed url, thanks to 
    // http://planetpeschel.com/wp/2012/03/how-to-add-a-twitter-rss-feed-to-google-reader/
    var feed = "https://api.twitter.com/1/statuses/user_timeline.rss?screen_name=" + canonical.substr(canonical.lastIndexOf('/') + 1);
    location = 'http://www.google.com/reader/view/feed/' + encodeURIComponent(feed);
}