Google Reader is probably the obvious choice when anyone thinks of feed readers. Bloglines, Netvibes etc. are also worthy alternatives. Being online applications, they can be accessed anywhere, and does not depend on the longetivity or proximity of your hard drive, ie. you do not have to worry about losing your feeds when you’re away from home or your hard drive crashes.
However, as Steve Smith of Ordered List noted, web applications still don’t behave like desktop applications. Something as simple as dragging feeds across various categories, checking feeds rapidly (which I usually do when referring to posts for research) seems like a chore in a web application. Of course, you can use Gears with Google Reader and download all items for rapid reference, but that is like going from Ottawa to San Fransisco via Berlin, Rome, London and New York. Or maybe like shooting a fly with a Kalashnikov. Web apps are getting better, but there’s still no web app like a desktop app.
Using a desktop application can thus make you feel at home. Another benefit is that desktop feed readers are perfectly suited to low bandwidth situations (when you’re using a GPRS/EDGE connection hooked up from your mobile phone, for example).
Here is a compilation of best free desktop feed readers to help you choose a good one when jumping ship. Note that this is not just another huge list of desktop feed readers with just links and screenshots. These are apps that I have used (for those that I haven’t, I’ve linked to other reviews) and wholeheartedly recommend. Also, no application gets a spot in this compilation for the sake of bumping up numbers. If there’s a unique feature(s) that I liked, the app gets mentioned.
If you are already using a desktop feed reader, you might still want to take a look at these to see if there is a better desktop application. Below, there are two applications for Windows, two for Mac OS X, one cross platform application and one for Linux. Take your pick!
FeedDemon (Windows)
FeedDemon is an awe-inspiring feed reader from Nick Bradbury. Newsgator acquired FeedDemon, and FeedDemon joined NetNewsWire (free, Mac OS X) and online feed reader Newsgator Online. FeedDemon sports an MS Office-like interface, three pane reading, customizable keyboard shortcuts, synchronization with Newsgator for seamless feed reading on Windows, Mac OS X and online. Also read our detailed review of FeedDemon.
Download FeedDemon
FeedReader (Windows)
FeedReader is an elegant, clean RSS reader with all the usual features. FeedReader warrants a place in this list for having all the nitty-gritty features, and one feature that I have not seen much: option to keep FeedReader in focus when clicking on links in feeds and opening the pages in browsers. Usually, clicking on links in most feed readers will open up your default browser, and the browser will steal focus (interrupting your feed reading). Not so with FeedReader.
[Note: Before you point me to Tweak UI powertoy to prevent applications from stealing focus, let me say that I have tried it, but it did not work. FeedReader has a specific option to do prevent losing focus]
NewsFire (Mac OS X)
NewsFire is a premium feed reader for Mac OS X, sporting a two pane reading, attractive UI and Mail-like goodness. that was made free to download by its developer David Watanabe recently (see his blog post). Watanabe is also the developer of XTorrent (P2P app for Mac OS X), AcquisitionX and Inquisitor plugin for Safari (now acquired by Yahoo).
Download NewsFire
NetNewsWire (Mac OS X)
NetNewsWire is owned by Newsgator, who also owns FeedDemon. NetNewsWire and FeedDemon can synchronize with Newsgator Online, which means that you could read your feeds seamlessly across Windows, Mac OS X and even your iPhone. As with most other Mac OS X applications, the design is attractive and makes feed reading a pleasure.
RSS Owl (cross-platform)
RSS Owl is a cross-platform open source feed reader. It includes quite a few bundled feeds sorted into categories. It supports bookmarking feed items and podcasts. RSS Owl is available for Windows, Linux and Mac OS X (FreeBSD, anyone? 
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Download RSSOwl
Liferea (Linux)
Liferea and RSS Owl are two credible desktop readers for Linux. RSS Owl has been blasted by many for being coded in Java (hence being resource hogs). If you are one of those criticizing RSS Owl, Liferea is worth trying. It is a fast, lean feed reader with minimal library dependencies.
Honourable mentions that did not make the cut for this post: SharpReader, RSS Bandit and GreatNews RSS readers. Linux users might also want to try Straw or Akregator (KDE).
Among other reasons, desktop feed readers are blazing fast as compared to their online counterparts. But if you are one of those lucky souls with a 16 Mbps FIOS, then any online feed reader would feel like a desktop application.