Windows: Quite a few instant messaging clients feature Facebook chat integration, but fTalk aims to provide a minimal, lightweight desktop client for Facebook chat without the hassle of juggling other accounts.
Since you don't have to keep your browser open, fTalk is a good way to stay connected while losing the distraction of status updates. It also keeps its interface the same, so if you're bothered by Facebook's recent change in its browser chat, this will solve the problem. The simple interface and lack of unessential features means the memory stamp is pretty low and it's easy to setup. While the features are bare, you can set notification options, including sound and system tray alerts depending on how or if you'd like to be notified.