SharpDevelop is a free as in beer substitute to having to pay for the less than free as in beer Microsoft Visual Studio .NET Integrated Development Inviornment. It comes with almost all the features and functionality as VS.NET and you don't have to worry about hawking over a copy to your friends and professors.
The Eclipse IDE for java is Free as in beer and it is one of the most amazing IDE's that is far superior to anything that is less than free as in beer. Their newest build 3.0 is amazing and is on par with MS VS.net
Pork is an Open Source Instant Messenger client for AIM which runs via a console.
Gaim is an Open Source application for linux which functions as a Instant Messager client for AIM/ICQ/YIM/MSN
This is the Instant Messagingapplication for AIM/ICQ/YIM/MSN which i use on a regular basis for MS Windows XP SP1
This is the NAT/router script which i use to give everyone internet in my house, i love it to death,
and garric is da bomb 
w00t..