What a week for the LAMP stack!
PHP 5.4.0 has been released. You can view the complete change log here and then be sure to check out the migration guide as there is a whole swathe of compatibility breaking changes.
MySQL 5.5 has been released. Probably the most exciting new features in this version are the making of InnoDB the default storage engine and semi-synchronous replication
Apache 2.4 has been released.
And in other news...
Ruby 1.9.3-p125 is out if you are that way inclined.
Speaking of Ruby, the prolific Zed Shaw has a great resource for learning regex the hard way. Regular expressions are endlessly useful and a must have arrow for your quiver.