I presume you use Google Analytics. You can easily generate links to tag external links in GA. Look for http://www.google.com/support/googleanalytics/bin/topic.py?topic=11096 You would need to use URL Builder to generate links which you can use in your RSS feed. You probably also would need to use Feedburner or something similar to edit your feeds. If you are stuck give me a shout.
Thats really not 'nice' if you want to count them, feed readers are feed readers and general visitors are just general visitors! Why would you want to count them anyway?