Googsystray is a system tray app for Google Voice, GMail, Google Calendar, Google Reader, and Google Docs. It lets you keep track of the information provided by those services without having to keep a bunch of Web pages open or constantly checking them. It notifies you of new events, such as messages or alerts, and provides basic services quickly.
wmsystemtray is a system tray using the freedesktop.org system tray protocol that was implemented as a Window Maker dock app. It has the ability to display more than one dock window to make room for more tray icons, and the ability to scroll through the icons if more are present than will fit.