Aiarsi

IRC stands for Internet Relay Chat, and it is a protocol that is widely used for setting up communication channels where users can join with ease.
Since it is a popular protocol, there are many desktop applications that simplify the task of connection to such a channel, and Aiarsi is one of them.

A portable IRC client

Since it is a portable utility, you do not need to install it on your computer, meaning that no new registry entries are created. However, you need to enable the Portable Mode checkbox from the Settings window to make sure you fully enjoy this out-of-the-box experience.
This application is meant to be as straightforward as possible, so as to encourage all users to connect to a server, join a channel and send messages to the group.
Briefly put, you only need to specify the host address, the port number and encoding type, and then choose a nickname and a password. You also get to assign a relevant title to each channel, so you can identify them easier in the future.

Join channels and start chatting

Once you entered the address of the server you are interested in, Aiarsi allows you to get the full list of available channels and you can select the one you prefer.
After you joined a channel, you can start sending messages to the other users regarding the currently discussed topic. Additionally, you can run WHOIS on any selected user, as well as ping them with as much as a mouse click.

Minimalistic, yet handy app

The application can be set to run directly in the system tray, so it does not disturb you from your work. Alternatively, it can be shown in the taskbar with the app name you prefer.   
When it comes to notifications, you can choose between playing a sound or displaying tray balloons, whichever suits your needs best.
All in all, Aiarsi is a nifty piece of software that is specifically designed for all those who value simplicity more than anything else.