I generally use Kopete for instant messaging along with Choqok for microblogging. However, I spotted a useful post on The Linuxologist, regarding adding Facebook contacts to Pidgin and I decided to add a bit to it from my experience. In case you don't use any microblogging clients for your platform then it might be useful to add those services to Pidgin if you use Twitter or Identi.ca often.
This is especially useful to non-KDE users who prefer Pidgin as their default IM. Facebook support in Kopete is in the development stage and pre-release instructions are available here. I've tried installing it via AUR using this package, but I haven't been able to get it to build completely yet.
Adding Facebook support to Pidgin is simple. The pidgin-facebookchat plugin should work fine. If you use Arch Linux, there is a package available in AUR here. It is part of the community repo so pacman -S pidgin-facebookchat should work fine. If you run Ubuntu or a Debian-based distribution, there is a .deb package available on the plugin page as well. You can also download the Facebook icons pack so that you can identify your Facebook contacts in Pidgin. Instructions are available here. Make sure you have the requisite packages for .zip compression support in your distribution. In Arch Linux, they are zip and unzip.
Twitter / Identi.ca
To add support for microblogging services like Twitter and Identi.ca you simply have to install another plugin, microblog-purple. There is a package in the Arch Linux community repo available here, so you can install it with pacman -S microblog-purple. For Windows users again, there is an executable file. Mac users can integrate this plugin in Adium, as per the Readme on the plugin page.
