werty - 2:11 pm on May 3, 2005 (gmt 0) So the short answer: there is no easy way that I know of.
This has always been a problem. The one solution I know of is feedburner, another would be to look at your logs, but this shows the various news aggregators that will hit your feed as well as a request each time they come around(sometimes every 20 minutes). You can log in to bloglines and see how many people subscribe to your feed on there, but that is only limited to blogline subscribers, which has a limited marketshare.
So the short answer: there is no easy way that I know of.