On this page I'll try to keep a compiled list of most popular RSS feed readers, ie. desktop and online applications that are mostly used for reading RSS feeds. There are still no reliable ways for determining this (and it's questionable whether there will ever be), so I will be gathering this information from various sources, all of which will be listed with the stats. The most reliable source is currently FeedBurner since it has stats for a large number of feeds.
Information about the RSS reader market share can be quite skewed by online aggregators. For example, if you've used Bloglines for a while and then abandonded it while leaving your feeds active, Bloglines will still keep you marked as a subscriber and this will count in FeedBurner stats. Care should also be taken to eliminate the frequency of updates, so that unique visits are counted and not each and every hit. FeedBurner supposedly takes care of this.