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.
GCalert will access all your Google calendars and display alarms via libnotify for whenever you have alarms set for each event. These alarm widgets do not receive focus (and thus do not take keyboard input away from other applications), yet are clearly visible even on a cluttered desktop.
Emaigos imports Google contacts and calendars into Emacs. Contacts are stored in a Big Brother Database (BBDB) file, which makes them usable with many Emacs email packages, like Gnus. Google calendars are stored as a single Org-mode file, so events may be viewed as a structured document and possibly shown within an Agenda view. With Emaigos, it's possible to use Google as a contacts and calendars manager, while having all the same data available within Emacs. The original Google contacts and calendars are not modified in any way by Emaigos. The name "Emaigos" is an acronym for "EMAcs Importer for GOogle Stuff".