Plugins that start with the letter Z, are Free and are sorted by Rating (descending).
Zoo Zeebra is a very simple plugin that adds first and last classes to your lists/entries. It also adds classes for certain intervals (default 2, for odd and even rows).
A quick and simple way to add zipcode searching to your EE. (U.S. Only)
zodEEac is a plugin to output Zodiac Name or Symbol for a given date field. The date field can be EE2 channel date field or a custom channel field or any date.