jQuery team announced a major release yesterday. It is about 49% faster than previous engine. The big features of this release are:

• Sizzle: A sizzlin’ hot CSS selector engine.
• Live Events: Event delegation with a jQuery twist.
• jQuery Event Overhaul: Completely rewired to simplify event handling.
• HTML Injection Rewrite: Lightning-fast HTML appending.
• Offset Rewrite: Super-quick position calculation.
• No More Browser Sniffing: Using feature detection to help jQuery last for many more years to come.

The full details of the release can be found in the release notes:http://docs.jquery.com/Release:jQuery_1.3