Apple on Friday released Mac OS X v10.3.6, an upgrade that offers improvements in several areas of the operating system, including added compatibility with FireWire audio and USB devices; updates to the Calculator, DVD Player, Image Capture and Safari applications; improved OpenGL video technology, along with updated ATI and NVIDIA drivers; improved file sharing in Mac (AFP), UNIX (NFS) and PC (SMB/CFIS) networks as well as more reliable network auto-mounting and launching of network applications; and more. You can find this download by running Software Update in System Preferences or by visiting a page in Apple's Knowledge Base that links to the stand-alone installer.
Download size (14MB to 34.6MB) appears to depend on the requirements of each machine, with Apple designating the update as a 'Delta' release. For more on this, and the chance to contribute yourself, read the special Macworld Forum thread here.
In addition, the company made Mac OS X v10.3.6 Server available. It includes everything found in the Mac OS X update and adds improvements to Open Directory, File Services, Fibre Channel Utility, Mail Server and LDAP. You can download the installer from Apple's Knowledge Base or use Mac OS X Server's Software Admin utility or the "softwareupdate" command-line tool.