I use MainMenu, a great little utility to use for regular and preventative maintenance on your Mac. When you start it up, it will show up as an icon in the menu bar to the left of the Airport icon.
Then you can pull down on the menu and select what you want to do, i.e., repair disk permissions, run the middle-of-the-night periodic tasks anytime, clear font caches if you have text display problems, and much more.
The only problem I have with MainMenu is lack of much help or documentation. You need to already know what many of the functions are and what they do with OS X before you dive into using them.
But, you might find the “Relaunch Finder” feature handy. If you’ve been using lots of windows and some won’t activate or appear empty when you open them, relaunch your finder, which is quicker than a full reboot.
One of the nice features is “Execute Batch Scripts.” You can set what you want to run and then run all the features at once. On my MacBook, I have these set up for batch: repair permissions, run all cron scripts, update prebindings, and empty caches. After you start up MainMenu, look at the “Preferences” for settings for running batch scripts.
You can’t hurt your Mac by running the utilities too much, but there’s no need to run them more than once a month, unless you have definite problems.
You can have MainMenu start up each time you use your Mac, which is what I do, so it’s there when you need it. Or, leave it in your Applications folder and double click it.
MainMenu has too many capabilities to cover here, so check out the overview when you download it at MainMenu, and get some help before you run some of the more technically oriented functions.
Update: 7/14/09 MainMenu is not free anymore. You can download and use the newest version for 15 days; after that, it’s $20 for registration.