Mac's don't need defragging as OS X automatically writes 2Gb or below sized files to one contiguous space on the drive. There are certain cases where's it's needed to free up a large spaces on the drive, but not something everyone has to do.
Check Your Disk to See What is Taking Up Space and Find Large Files. To free up disk space, it’s helpful to know exactly what is using disk space on your Mac. A hard disk analysis tool like Disk Inventory X will scan your Mac’s hard disk and display which folders and files are using up the most space. You can then delete these space hogs to. There are 2 popular removal tools for Mac with almost similar names – AppCleaner and App Cleaner & Uninstaller Pro. Although they have completely different interfaces, developers and functionality, they tend to be mixed up by most users. On some well-known download archives, I found user comments AppCleaner or App Cleaner & Uninstaller Pro?
Far as other Mac maintainence, there really isn't any except to backup one's files regularly. Keeping Software Updated and run a web browser check to make sure the plug-ins are current.
For Safari and Flash, this check is more accurate
Most of those cleaning programs are junk, especially MacKeeper.
Pocketbits Disk Cleaner
If your friend got onto your computer and visited a bunch of adult sites, then I would recommend something like OnyX, doing ALL the cleaning and maintenance aspects and rebooting, perhaps followed by a Disk Utility Erase free space.
CCleaner beta is out for OS X, used on PC's and combines cleaning and scrubbing of the drive if setup correctly.
Disk Cleaner Pro Mac
If your interested in performance, read my post here
Oct 1, 2011 12:37 AM