Adium, the Mac-based instant-messaging king
Adium is the best chat client available for the Mac OS. Period. It also happens to be 100 percent open source.
Given all the great consumer-facing open-source software available, I figured that I'd try to evaluate and write reviews on those I use most often. Open source long ago stopped being about developers for other developers. Here's proof.
Adium is quite simply the best instant-messaging (IM) client available. Period. It has its flaws and is, in some ways, deficient compared to iChat, Apple's own IM client. But its strengths vastly outnumber its weaknesses. I've been using it for years. In some ways, it's very similar to Trillian on the Windows platform in that it allows you to combine nearly all of your IM services (Yahoo!, MSN, AOL, Jabber, etc.) into one client.
But Adium actually goes further and provides more.
I initially resisted Adium because, well, I'm not fond of ducks as program icons. But then I discovered that I could dress the duck in an Arsenal uniform, and the resistance crumbled. When I discovered that my Arsenal Adium duck could also wave Arsenal banners, I became an Adium devotee. It has been one big devotional ever since.
It is in this area of customization that Adium proves its open-source credentials. Successful open-source projects tend not to necessarily garner a lot of outside code contributions to the core of a project (85 percent of core development work is done by a core development group of fewer than 15 people, on average), but rather invite a robust community "at the periphery." Language packs, add-ons, etc.
This is emphatically true of Adium, which has an amazing array of third-party add-ons or tweaks called Adium Xtras. This is where I found the Arsenal "skin," and it's where you can make your dock icon juggle and do just about anything (or look like just about anything). I actually purposefully decided not to include a screenshot because there is no shortage of ways to customize the appearance of Adium--how I have configured it would tell you nothing about how you could (or would).
But Adium is more than a pretty face. It provides for near-infinite tailoring of the user interface to make the buddy dock and chat windows look and behave as you wish. You can also choose from a wide array of sounds to use with the program. I use "Tokyo Train Station," which often causes my kids to head to the front door to see who rang the doorbell.
Beyond appearance and sound, I mentioned above that Adium supports just about every chat protocol you can imagine:
The only one missing that I dearly wish were there is Skype, as I tend to use Skype IM quite a bit, as it's the one "neutral" platform that I've found for IM between Mac, Windows and Linux users, AOL Instant Messenger (AIM) being the second most common platform used. But many of Alfresco's developers, for example, refuse to use AIM, so Skype becomes the standard. Unfortunately, Adium has no Skype support.
Adium allows you to initiate and hold group chats, display your status in a variety of ways (including my favorite: iTunes status (displaying song, composer or whatever you want), use emoticons specifically tailored to the chat platform you're on (i.e. choosing to use AIM-specific emoticons or a broader set when using the AIM protocol on Adium) and do file transfers.
It is in this last area, however, where Adium proves its fallibility. I often have file transfers roll over and die in Adium. Other weaknesses? It's available only for the Mac (which is great if that happens to be your platform) and doesn't offer audio or video chat (video chat with Apple's iChat is fantastic - dramatically better than anything else out there, whether Mac, Windows, or Linux-based).
Even so, for straight chat on the Mac, there's nothing better. It's 100 percent free, as in price tag as in license: GPL version 2. If you use IM, you need Adium. If you are stuck on Windows, well, buy a Mac.