Recently, Andrew Goodman posted the following to his blog about counting RSS feed stats:
"One interesting trend is the increase in what we believe might be regular readership via RSS feeds. I suspect the analytics services need to buckle down and offer a better breakdown of those kinds of visitors. What if someone has syndicated this blog on their Firefox browser? Would that show up merely as a direct navigation similar to visiting via a bookmark? Probably."
Yahoo has an answer for you. They put your RSS feed stats in their User-Agent. (See here: http://publisher.yahoo.com/track.php). So you can look in your logs and find lines like this:
220.127.116.11 - - [23/Mar/2004:08:13:30 -0800] "GET /blog/rss2.xml HTTP/1.0" 304 - "-" "YahooFeedSeeker/1.0 (compatible; Mozilla 4.0; MSIE 5.5; http://my.yahoo.com/s/publishers.html; users 236; views 36994)"
This would be the number of subscribers who have their feed on their MyYahoo page and the number of times they clicked on one of your articles. You could also get this info by counting referers from my.yahoo to your page.
Anyway, If you've got RSS feeds, try doing a grep on your web server log file for "YahooFeedSeeker"