This new post on DynamicWebPages.de today has information about the latest release candidate for the PHP 5.1.x series - version 5.1.3RC3.
Ilia Alshanetsky has released RC3 for download. The few bugs that were found (in RC2) were what made this release needed and they have been corrected. All of the changes are listed in the CHANGELOG file, and you can download the source from Ilia or the binaries from Edin Kadribasic. Be sure to test this one well - if no more errors are found, a final release could be as soon as next week.