TinyCal is a menubar calendar with Google Calendar integration. It can show multiple months, use custom calendars, and show holidays and personal calendars.

Features:

• Personal Google Calendar integration
• Support for Google Calendar Gadgets
• Configurable month display
• Configurable event display
• Custom calendars
• Tear-away menu
• Growl reminders
• Create and delete events
• Hot keys
• ISO 8601 week numbers
• Secondary calendar overlay 

• Multiple Months: TinyCal can be customized to show 1, 2, 3 or 12 months at one time. The display can be arranged as tall or wide.
• Google Calendar: TinyCal can display public Google Calendars for holidays for 40 different countries, from Australia to Vietnam. It can also display events from your personal Google Calendar. The following screenshot shows holidays from the USA in blue and a personal calendar in red.
• Custom Calendars: TinyCal can be customized to show other calendars, such as Buddhist, Hebrew, Islamic, and Japanese. The following screenshot show the Hebrew calendar with Jewish holidays.
• Tear-Away: The TinyCal window is a tear-away menu that can be repositioned anywhere on the screen.
• Today's Events: In the TinyCal window, today's date is circled. In addition, if there are any events occurring today, they are reflected in the menubar icon. In the following screenshot, the blue triangle in the lower right indicates that there is an event today.

Requirements:
OS X 10.5+
Intel