DynamicWebPages.de has a pointer to the latest beta for PHP 5.1.0 - PHP 5.1.0 Beta3 (released back on the 15th).

Andi Gutmans published today a third beta version of the coming PHP5.1.0 version for testing. If no more critical errors emerge, this Candidate ready to become the first release - so, get testing

The new version of PHP will contain a significant improvements in performance and PCRE5.0 Support apart from the PDO support as well as new functionality and bug-fixes, particularly regarding SOAP, SPL and Streams.

You can get the download here...