There's a Utilities folder in the Applications folder which holds some pretty cool apps that I reckon you might be interested in. I'm not much of a power user so I'm not sure what they all do but I know there's a Disk Utility app, among others. Is this what you're looking for?
Your starting point is the Disk Utility program that comes with your OS X (in the Applications: Utilities folder) It will Repair Permissions and it will verify and repair a drive (you may have to boot from the OSX CD to run Repair on your boot drive.) Repairing Permissions is a general preventative measure that you can do before and after installing new software... (although it does somthing completely different, you can think of it like rebuilding the Desktop on an OS9 machine if you are famliar with that)
A Mac hard disk generally does not need de-fragmenting (Speed Disk) because OSX runs maintenance routines of its own when you leave the machine on overnight.
If you run into major-league trouble with a volume's structure, the big guns are Alsoft DiskWarrior and Micromat TechTool Pro. TechTool Pro does more in the way of hardware diagnostics, but DiskWarrior is the most powerful resurrector of corrupted hard disk catalogs.
Note: Do not use Norton SystemWorks for Mac on an OSX machine, there have been too many cases of data destruction (2 in my own experience) directly attributable to the Norton products.
ProSoft DataRescueX is the program for recovering files from a damaged drive. However, there is no real Un-Delete function in OSX for files that have been trashed and the trash emptied, because OSX tends to over-write the disk sectors very quickly. There is a program, ProSoft DataRecycler, which if you run it *before* you have trouble, it keeps track of deleted files and can give you some recovery.
There are a variety of shareware programs available, many of which give a friendly interface to maintenance utilities that are already there in the UNIX underpinnings of OSX. Some popular ones are: Onyx, Cocktail, CacheOut X
Search www.versiontracker.com for information, latest versions and manufacturers' URLs on all of the above programs.