TinyCal is a menubar calendar with Google Calendar integration. It can show multiple months, use custom calendars, and show holidays and personal calendars. The basic version of TinyCal is free. You can use it as much as you like with no time limitations or obligations. Advanced functionality is available for $10. The full version offers the following features:

• Personal Google Calendar integration
• Unlimited public Google Calendars
• Customized event colors

Version 1.6:

• Create event loop fixed.
• Other bugs
• Versions now for Shareware (in the Plum Amazing store) and App Store (when they get the review finished).

Requirements

Mac OS X 10.4 or later, PPC 32