I strongly recommend Minco, which has tons of customisation features, but sits quietly in the menubar.
In fact, it's SO unobtrusive that I sometimes forget to use it!
But very slick app, and has a free trial if you download from the developer's website at http://www.celmaro.com/minco/
It's also available on the Mac App Store.
I'm not affiliated -- I just think it's a great product because it looks awesome, works very well and has plenty of hooks into iCal (and options for logging activities to calendars and even dynamically writing a text-file that can be imported into a spreadsheet or other apps later)
Very nice app.