Since March, there has been a wiki at wiki.php.net. The most interesting section is probably wiki.php.net/rfc, which - as the name implies - contains RFC's for improvements of the language. I've rambled on about closures and lambdas before, but as you can see, there is now an accepted patch. Whether it'll make it into 5.3 is unlikely at this point, but it looks like it'll at least be coming with 5.4 and/or 6.0.

He also points out the php-internals mailing list and the summaries that Steph Fox has written up weekly about the list's latest conversations.