I've been using the online feed reader Bloglines for few weeks now (replacing my previous favorite Feed on Feeds, which was hogging the resources on my web server). It's fast and very usable, but I was wishing for the same feature as Matthew, namely the feeds with new entries be sorted to the top. Otherwise, if you have several hundred unread entries (like, if you went to sleep for the night), you quickly become lost and the temptation is great to Mark All Read and start over. Lo and behold, Bloglines has added just this feature, and many more. And it's still free, although I'm sure that now that it's become indispensible, it won't be for long.