As is mentioned on PHP.net today, the first release candidate for the PHP 5.5.x series, PHP 5.5.0RC1, has been released for testing:

The PHP development team announces the availability of the first release candidate of PHP 5.5. This release fixes some bugs as well as some possible leaks from our last beta. This is a development preview - do not use it in production!

Some of the more major changes in this release include an update to the FPM SAPI for QUERY_STRING, a fix for a build issue with libgd, bugs in SNMP and a problem with stream_select on Windows x64 systems. You can find the full list of changes in the NEWS file. Please download and test (Windows binaries here) this latest release to help the development team find issues and move along with the PHP 5.5.x releases.