- QuickCal: inexpensive app. It has a configurable view where you can select the number of days as well as the number of tasks that you want to be shown in the menu. It allows you to create both tasks and events by typing kind of natural language. You need iCal running to get the events sync with your calendars. In the next version 2.5 there will add Google Calendar integration. I really like the task handling feature.
- Fantastical: probably the most impressive app by far. Amazing user interface, natural language recognition, nice user interface, etc. It also allows you to sync the events with CalDav calendars even if iCal is not running as it has its own implementation of CalDav for when iCal app is closed. What I dislike: price and no support for tasks.
- CalendarBar: nice app that supports iCal, Google and Facebook calendars. Nice integration with Facebook and also support for Growl notifications. It also handles tasks. The app only allows you to view events/tasks, not to create/edit/delete. Paid app, but not expensive.
- Calendar: Nice month view with week numbering. Color badges with the number of events per calendar. Again, it is a view-only app, does not allow to create/edit/delete events. The best of all, it is free.
- FlexCal: although this is not a menu bar app, it is very useful. It stays in your control panel and it allows you to easily create events/tasks with an easy keyboard shortcut.
And what I am using right now: a combination of QuickCal and FlexCal. I like the way QuickCal shows in one click everything that is coming next, both events and tasks. But I do not like the way to create events/tasks as I need to customize reminders. For that I use FlexCal, that has an easy way to select dates with a small month browser. You can actually use any of the view-only apps in conjunction with FlexCal to input events/tasks.
Besides these tools you can also have a look at TinyCal and MenuCalendarClock. I have been using them in the past. I was even a registered user of MenuCalendarClock, but I stopped using it because all the main updates were paid ones and I had the feeling it was too much paying for a single app.
Let me know your experiences and what suits you better.