DynamicWebPages.de has a note today about the posting of PHP 5.1 Beta version 2 over on the main PHP site's download page.

This second beta eliminates the problems with PDO that were seen in Beta 1 (due to communication issues between developers). All of the PDO-related issues from Beta 1 are corrected, however, along with a few other smaller bugs - mentioned in the news file. So, get on over there and get to testing this beta so that the final release will come that much sooner!

It looks like they also made some improvements while they were in there, including a rewrite of strtotime to "support timezones and many new formats"...

From the main PHP.net page:

PHP 5.1 Beta 2 is now available! A lot of work has been put into this upcoming release and we believe it is ready for public testing. Some of the key improvements of PHP 5.1 include: PDO (PHP Data Objects) - A new native database abstraction layer providing performance, ease-of-use, and flexibility. Significantly improved language performance mainly due to the new Zend Engine II execution architecture. The PCRE extension has been updated to PCRE 5.0. Many more improvements including lots of new functionality & many bug fixes, especially in regards to SOAP, streams and SPL.

See the bundled NEWS file for a more complete list of changes. Everyone is encouraged to start playing with this beta, although it is not yet recommended for mission-critical production use.