Ding!  If you're still using AOL's default instant messenger (or Google Talk, or Yahoo! Messenger, or...), then you're missing out on a wide range of alternative features--more than you perhaps though possible in a common messaging application.  Or, worse, you're trying to converse with your friends across the various networks by using three or more individual applications at once.  While this might have been the only way to bridge the gap between these services before, you can plead ignorance no longer.  Start the uninstaller--and this article--and by the time you're finished with both, you'll never go back to the antiquated world of official messaging applications.  Third-party is where the real party's at.

What can you expect to find in these open-source and freeware apps?  For starters, an interface that combines a number of common messaging networks into a single program.  In some cases, you can even lump your friends' various online names across the separate chat networks into a single, unifying alias--click a drop-down box to specify which network you want to reach them on.  Beyond that, these programs can bring a number of plugins and external connections to the table.  Combine your Facebook and Twitter feeds into your friends list, find out when people are about to message you before they do so, and call your buddies through your messenger interface akin to Skype.  And that's just the tip of the IM iceberg.

Pidgin

What it does: I don't often play favorites in the freeware roundup, but I've been a steadfast Pidgin user for the past few years and can find little wrong with this lightweight, plugin-packed app.  Out of the, er, box, Pidgin supports a comprehensive list of chat networks: AIM, ICQ, Google Talk, Jabber/XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, MySpaceIM, and Zephyr.  You can add more by downloading plugins for Pidgin, although you'll find a wealth of usefulness in the customizable add-ons that the application already builds into its default installation.  My favorite?  Check out, "psychic mode," which pops up a blank IM window whenever someone is about to send you a message.

Download it here!

Digsby

What it does: Were Pidgin to have a full-fledged rival, I would put Digsby at the top of the list.  What it lacks in cleanliness and unobtrusive installation mechanisms, it makes up for in total network comprehensiveness.  Not only can you message your friends across a range of the most popular chat networks, you can also integrate your Facebook, Linkedin, Twitter, and MySpace accounts into the app.  Get your friends' latest status updates, messages, photos--the whole kitchen sink--the second they post them. Heck, you can even use Digsby to check and send email.  If you really, really hate the idea of having to fire up a few programs for multiple social interactions, switch to Digsby. It's the ultimate aggregator.

Download it here!

Trillian Astra

What it does: This one's still in beta, but it's every bit worth mentioning and/or playing around with. Aside from the common IM features that one would expect to find in a program like this, unique additions include: the ability to specify on a user-by-user basis who sees you as "online" or "invisible," a unique "Trillian profile" URL that you can share with friends instead of having to go through a list of your online handles, RSS integration and automated file transfer improvements, and integrated IRC support.  The downside?  A number of the super-cool features are locked away to the "premium" version of this application.  And by premium, I (and Cerulean Studios) mean "paid-for." Still, if the Digsby interface turns you off, then you might find more happiness in the comprehensive, free offerings of Trillian Astra.

Download it here!

Miranda IM

What it does: Simplicity, simplicity, simplicity.  If you don't have the time or desire to fiddle with a number of configurations, features, and plugins, then you might want to check out Miranda IM.  This no-fuss, no-installation IM application is a great program to stash onto a USB key.  Plug it in, fire it up, and you'll be ready to connect to AIM, ICQ, IRC, MSN, and Yahoo! chat networks, to name a few.  But don't think that you're always going to be restrained to basic IM functionality.  You can build additional features into your Miranda IM client by installing any of the 350+ addons currently listed in the main site's database. 

Download it here!

VoxOx

What it does:  Like Trillian Astra, the lesser-known VoxOx is still in beta as well.  And while it offers similar functionality to Diggsby, one of the stand-out features of VoxOx is its integration of a Skype-like calling functionality into the main program.  Your account comes with its own phone number for others to reach you at, and the application will even forward incoming calls to an external number of your choosing a la Google Voice.  A robust personal assistant allows you to customize your responses to incoming calls, including personalized responses for different contacts, call screening, and--my favorite--personalized waiting music.  If you want to share files with fellow contacts in VoxOx, your upload (up to 100MB) is converted into a download link rather than a direct connection transfer like other clients.  Although the software is free, calls cost $0.01 a minute for U.S. numbers.

Download it here!

David Murphy (@ Acererak) is a technology journalist and former Maximum PC editor. He writes weekly columns about the wide world of open-source and roundups of awesome, freebie software. Shoot him a message via Twitter, especially if you have an awesome app or game you're dying to recommend!