Martin Dougiamas recently posted on Moodle Announcements that latest stable releases of 1.8.x and 1.9.x are now available.

There are many small bug fixes and some new features in each release, but the main two things you need to know about are the gradebook interface changes in 1.9.5 and some important security issues. – Read more

Related Links:
Release notes for Moodle 1.9.5
Release notes for Moodle 1.8.9
Moodle 1.9.5 and Moodle 1.8.9 are now available – Martin Dougiamas post