Note for those new to feeds: Most blogs and other sites that regularly update content provide an RSS or Atom feed. This is an address you can paste into a feed reader such as the ones described here. In the upper right of this page, for example, you’ll see an orange icon similar to the one being held by Tux in the intro image. Right clicking that icon will allow you to select Copy Link Address or something along those lines, depending on your browser. Pasting the address into any of these feed readers will subscribe you to that feed, and all new updates from that site will be sent there.

Liferea

Liferea (Linux Feed Reader) is one of the more popular feed readers for Linux. It’s got all the basic functionality – easy adding and removing of subscriptions, folder support, and key-based controls.

One of the more interesting aspects of Liferea is its built-in Lua scripting support. Users can create their own scripts based on certain events in Liferea (startup, new items arrived, etc). The bad news is that this feature appears to be slated for removal in future versions.
Liferea also provides good Gnome integration by allowing you to reduce the program to a panel app. New and unread items will show directly on your panel, which can be clicked to restore the full UI.
If you’re new to feeds, or just want basic functionality in your reader, Liferea is a great choice.

aKregator

There are, of course, options for KDE/Qt in the world of feed readers. Among the best is aKregator. It continues the KDE habit of high functionality, and includes some great configuration options.

One of aKregator’s best features is that it lets you edit the settings of each feed individually. This means that you can do things like set update intervals for different times on different sites. Make Tech Easier typically updates twice a day, so it could be set to a 12 hour interval, whereas it may be more appropriate for a news feed to be set to a much smaller interval. This decreases wasted bandwidth for all, and is less likely to cause your Internet line to “hiccup” while many feeds update at once.
aKregator also integrates with the Gnome and KDE panels, displaying unread counts and allowing access to the program’s configuration.

BlogBridge

As a Java application, BlogBridge is not specifically tailored for Gnome, KDE, or any other desktop environment. BlogBridge calls itself “the ultimate info-junkie system”. In addition to the normal feed subscription options found in all feed aggregators, a free account from the BlogBridge website gives you online sync of your feeds and access to the BlogBridge Expert Guides. These are collections of feeds reportedly put together by experts in various fields. Everything from politics to programming to Vanity Fair can be found in the guides section. This alone may make BlogBridge worth mentioning, but the application itself is a fully capable feed reader.

The dotted graph next to each feed name indicates the amount of traffic coming from that feed. In the above screenshot, you can see that BorgBlog hasn’t been updating lately, and that Mike Lynch doesn’t work on weekends.
Instead of organizing feeds by folders, you create your own Guides, which are once again just a collection of feeds. This can be done by browsing through BlogBridge’s fairly extensive library or by adding your own feed addresses manually.
Finally, if you’d like to find out if you’re one of the “info junkies” they’re talking about, you can pull up statistics from Tools > Statistics to see just how much time you spend on your feeds.

Honorable Mentions

Bottom Feeder and RSSOwl are two other popular options for Linux feed readers, however neither would run properly on the Ubuntu 64 bit test machine, so they were considered unsuitable for review. If none of the above options meets your needs, one of those two might be what you’re looking for.
Have you found any Linux feed aggregators better than the ones listed here? If so, let us know in the comments.