For OC Muggers, official OnyX for Leopard is now released: OnyX is a multifunction utility (maintenance, optimization, and personalization). It allows you to verify the Startup Disk and the structure of its System files, to run misc tasks of system maintenance, to configure some hidden parameters of the Finder, Dock, Dashboard, Exposé, Safari, Login window and of some of Apple's own applications, to delete caches, to remove a certain number of files and folders that may become cumbersome and more. Automatically check update, verify the status of startup disk and the structure of system files at launch, parameter with precision the actions, modify the appearance of OnyX, increase the window transparency, chooose its icon and the toolbar icons among those proposed in the Preferences... Requirements: OnyX is an Universal Binary application and works with all Macintosh PowerPC and Intel computers running Mac OS X version 10.5 or later (Leopard). To run correctly, OnyX must be run from an admin account. Get it free here : http://www.titanium.free.fr/pgs2/english/download.html
Onyx is a more advance app than Maintenance and it does more than maintaining your mac. But both apps were made by the same companies. Basically, Maintenance is "included" in Onyx.