Here's a simple text replacement trick to find the number of people that have subscribed to any XML feed that's powered by Feedburner provided the feed publisher has enabled FeedCount.
Feeds on Feedburner have an address like feeds.feedburner.com/labnol. All you now need to do is prefix the feed name (labnol in this case) with ~fc/ so that the new URL looks like feeds.feedburner.com/~fc/labnol
You're done. Just click on the new URL to see the count of RSS subscribers. It points to an graphic image (in GIF format) which you can also embed in your webpages as you see below:
As on today, TechCrunch has 65K subscribers while BoingBoing has 1401K subscribers. You don't see the circulation statistics for ShoeMoney and PostSecret as they have not enabled FeedCount Chicklets in their Feedburner Publicize channel.