8 hours ago, WordPress 2.5.1 has been released. Ofcourse it includes a number of bug fixes, performance enhancements, and one very important security fix.
One highlight you can read upon visiting the page is about the SECRET_KEY. It is a new constant allowed in the wp-config.php file since WP2.5 which is meant to introduce a little permanent randomness into the cryptographic functions used for cookies in WordPress.
To get one, just visit this link and you will get a randomly generated unique key for every page load. Just grab one and add it to your config file to get that additional security.