I use the one available with Mozilla Thunderbird. Very convinient and free. The other RSS reader that I really like is Newsgator. But ofcourse, one needs MS Outlook for this as it is a plugin into outlook and then it is not free :-(
I just love the two pane style of bloglines and I simply love the email support it provides, and also the grouping feature. I wish I could get these three things in a desktop aggregator.When you've got thousands of posts waiting for you, you don't want a three pane aggregator.