Itsycal is a tiny menu bar calendar.

If you want, it will display your events as a companion to the Mac Calendar app. You can also create and delete (but not edit) events.

Alternative to BarTender?

AnyBar is a small indicator for your menubar that does one simple thing: it displays a colored dot. What the dot means and when to change it is up to you.

The BitBar app lets you put the output from any script or program right in your Mac OS X menu bar. And it's completely free. An impressive number of plugins have already been contributed by a wide range of developers just like you, and this site makes it easy to find them.