Slick is a free instant messaging client that allows you to talk online with your friends via the most popular IM networks.
Specifically, Slick lets you connect and communicate with friends on ICQ, Yahoo!, AIM and MSN Messenger. Besides just sending and receiving messages you can also add emoticons (not enough to choose from for my liking though), change your status and add new contacts.
Slick's interface is not too taxing to find your way around and owes much of its design to the popular IM clients. Thankfully, it also brings with it some of the more advanced features of these clients too, including the ability to share files, view chat history, and set up all manner of alerts.
If you're looking for a no-nonsense way of chatting with your IM contacts on the bus then Slick provides a, well, slick, means of doing so.