This release introduces changes to pledge recording and quite a few bug fixes; for full list of things that has been fixed/improved in 3.2.3, please take a look at our issue tracker.
Unfortunately a bug related to wrong case types being displayed was introduced into 3.2.3 release. The patch will be available in the next 3.2.4 release and could be downloaded here if you want it earlier.
For more details on major new features/highlights, please refer to 3.2 release blog post, here's the short list:
You can download the release from SourceForge – select from the civicrm-stable section. The filenames include the 3.2.3 label: civicrm-3.2.3. Make sure you’re downloading correct version: for Drupal or Joomla.
If you are installing CiviCRM 3.2.3 from scratch, refer to the installation guide:
The procedure for upgrading to 3.2.3 is the same as for upgrading to 3.0.x. You can upgrade directly from 2.2.x or 3.0.x or 3.1.x. Instructions: