Ubuntu comes bundled with an instant messaging client, called Pidgin.
Pidgin is a general-purpose client, which can connect to any of the following services:
Personally, I only use it to connect to MSN Messenger, because that's what I was using before I started using Ubuntu, but it will work with any of them.
It's important to note, however, that Pidgin is not a “lowest common denominator” instant messaging client. If there is a feature that MSN Messenger has that other services don't, or that AIM has, there's a good chance that Pidgin has it, too.
I should also mention that Pidgin isn't just for Linux; there is a Windows version of Pidgin, as well. And any of the settings, tips, and tricks on this page apply equally well to the Windows version as they do to the Ubuntu version.
If you're interested in Pidgin, you might also be interested in meebo.com. This is a web-based instant messaging client — built on the same open-source software that was used to create Pidgin — which you can use to log onto your instant messaging service(s) from any computer.
In most cases, setup is pretty simple.
I'm assuming that you already have an account (or multiple accounts) set up with various services, such as MSN Messenger, AIM, etc. If you don't, you'll need to set up your account(s) first, with the appropriate service(s). You can't create an account from Pidgin.
Open Pidgin, and go to the Accounts->Add/Edit menu. If you had already added any accounts, this is where they would be listed.
More than likely, if you're reading this, you haven't yet added any accounts, so Pidgin will tell you this, and invite you to create one. You will then get this dialog:
Choose your service from the drop-down. Depending on what service you're using, the different fields you need to fill in will be different. For example, for my MSN Messenger account, the settings look like this:
In this case, the the Screen name will be your user ID (normally your email address), while the Local alias is what I call your “display name,” that will show up when others have you on their contact list. (Password is self-explanatory.)
In many cases, this is all you'll need to do, and after you save these settings, you're up and running. Pidgin will connect, and display your contacts. If you have multiple accounts with multiple services — or even multiple accounts with the same service — you can add them all. All of your contacts from all of your services will be listed.
If you're using Pidgin at work, and it doesn't work, you might be behind a firewall. See the instructions below, for some helpful tips.
Setting Up Pidgin for a Firewall
Although I found Pidgin took no configuration to work at home, it did take some configuration to function at work, where there are corporate firewalls and/or proxy servers to get through.
All of the settings for getting Pidgin to work through your corporate firewall are done through editing the settings for a particular account. So, from the main Pidgin window, use the Accounts->[account name]->Edit Account menu, to bring up the settings for your account. Then go to the Advanced tab.
In most cases, simply telling Pidgin to use the “HTTP method” is probably enough; you shouldn't have to fiddle any further with your proxy settings or anything, just use whatever is configured for GNOME overall.
Also, if you are working on a laptop, which you use at both the office and at home, then you have to remember to undo these settings, whenever you're working at home.
Helpful Hints: The Esc Key
Actually, I only have one helpful hint: Using the Esc key, to exit from a conversation window. I'm used to MSN Messenger, where you can use Esc to close a window, but by default, Pidgin doesn't allow this. You can turn it on, by following these instructions.
First, you need to shut down Pidgin. Then go to your home folder, and find the .purple directory. (Notice the period — this directory is hidden. If you're using Nautilus, you'll need to display hidden files, in order to see it.) In this directory there may or may not1 be a file named accels. If the file exists, edit it, and it if doesn't, create it using your favourite text editor.
You need to make sure that the following line exists somewhere somewhere in this file:
(gtk_accel_path "<main>/Conversation/Close" "Escape")
Again, if the file already exists, this line will probably already be there, with a ; character in front of it. If so, simply remove the semi-colon. (This will “un-comment” it.) Otherwise, you can create the file with just this one line in it.
Once this is done, re-start Pidgin, and when you're in a conversation window, you'll be able to use the Esc key to close it.
If you're curious, and want to look at the accels file again, you'll notice that Pidgin will have actually filled it out, and put all kinds of stuff in there. But it will leave your Esc accelerator in place.