-Wano
There are some things you could do in OS X for "System Maintenance". However, in OS X it's probably more accurate to call it "Preventative Maintenance"
One thing about OS X is that it won't suffer from clog-down - that pesky habit of Windows getting slower, and slower, and slower as the registry fragments, and .tmp files build up (theres more to this, but I don't wish to digress further).
So, you really shouldn't see much performance degradation in OS X even without "System Maintenance", but it's still a good idea to do once and a while.
One good package: DiskWarrior 3. Coming soon.