Apple has issued two updates, one for the MacBook Air, the other for the Mac Pro.
MacBook Air SMC Update 1.0 is recommended for all MacBook Air owners and is a 551k download. The SMC Update fine tunes the speed and operation of the internal fan and is available here.
The ATI Radeon HD 2600 XT Firmware Update is available either through the Software Update system preference or directly from the company support website.
The update is for those Mac Pros that include one or more ATI Radeon HD 2600 XT graphics cards installed. It's designed for use with Mac OS X v10.5.2 with the Leopard Graphics Update installed.
The update 'improves system stability,' according to Apple.