With Leopard and prior versions of OS X, one of the popular maintenance utilities was AppleJack, which is a free SourceForge project and ran in the Terminal (preferably Single User mode) as an easy-to-access way to run a bout of cleaning functions on the Mac. AppleJack so far has been incompatible with Snow Leopard, but with today's update the Snow Leopard incompatibility has been squashed.
After installing AppleJack, you will be able to run it by booting directly into Single User mode (hold Command-S) at start-up, which will drop you to a command line with root privileges. From here you basically enter "applejack" and follow the onscreen instructions to perform a number of maintenance routines.
Instead of booting into the OS X GUI and loading a number of applications and system elements, simply dropping into Single User mode and running the program in auto mode will easily fix various problems and then reboot the system normally.
AppleJack was a good program for prior versions of OS X, so let's hope it keeps its reputation for Apple's latest OS. Let us hear your impressions of the latest version of AppleJack in the comments below. You can download AppleJack 1.6 from its SourceForge project page.