Had been using Pidgin very long time for both my office and personal IM accounts. One missing feature that i never noticed was missing notifications when a buddy comes online or goes offline. Started searching and came across Guifications, a plugin for pidgin that will show a popup for a number of configurable events. Guifications can be downloaded and installed from the following location.
It notifies you for a lot of events but what i wanted was when my friends login and logout of their IMs. I default popup that notifies failed to impress me, so started searching some themes for Guifications and found a lot of cool and colourful themes in the following link.
Installation of theme is easy, all you have to do is to unzip and place the folders at the correct location. In windows it is the following directory
<PIDGIN INSTALLATION DIR>\pixmaps\pidgin\guifications\themes
If you have the habit of displaying the song you hear as the status, musictracker plugin will help you in doing so in Pidgin. Check out http://code.google.com/p/musictracker/ for information about the same.