On the main PHP.net site today they've posted an announcement about the latest Release Candidates for upcoming PHP versions of PHP 5.2.1 and PHP 5.3.0.

The PHP development team is proud to announce the second release candidate of PHP 5.2.10 (PHP 5.2.10RC2) and the third release candidate of PHP 5.3.0 (PHP 5.3.0RC3). These RCs focuses on bug fixes and stability improvements, and we hope only minimal changes are required for the next candidate or final stable releases.

Both for maintenance and the only changes that should come out of them are small fixes prior to the stable release of both. You can grab these latest release candidates from the PHP.net QA site to test on your own machine. You can also grab the Windows binaries here.