What's the Mac equivalent of Windows' Turn Windows Features On or Off?
The Mac OS doesn't directly have a feature like this, mainly due to how the OS and supporting Applications are separated differently than Windows. 

Looking a while back, Microsoft was having some issues with anti-trust lawsuits, and the inability to really separate IE from Windows. From how I understood it, part of this feature (at least the user facing side, not the server side) was enabled to help users 'Turn off IE'. 

This grew on Windows two ways - one to let users 'remove' features that they didn't want to use, and two - to enable and disable server or other components. 

Following the first of the above - this is much easier on the Mac - just drag the Application to the trash. Don't want to have iPhoto on your machine, just delete it. You can always reinstall it later from the media or Mac App Store. While certain API's do tie into different Applications (think media browsers in Pages, etc), the OS doesn't have to always have these applications to run. And to my understanding (although I have never tried it), you could theoretically remove iTunes or Safari if you wanted (although, WebKit is still being used, and may require Safari). 

As for the second item above - server or other features - this is also much different on the Mac. For the actual server functions (outside of the Unix tools), you now just buy an app from the Mac App Store (you used to buy a different version of the Mac OS that was much more expensive). On Mac OS client, there is no direct way to fully remove a feature, say apache, without deleting the binaries, etc. from the actual UNIX paths. So, in this case, there really is not a direct correlation on the Mac OS. 

When it does come to certain 'server-like' features in the Mac OS (for example setting up file shares, ssh, etc), these are under System Preferences -> Sharing. 



Finally, the Mac OS tries to be a bit smarter about this too. Take for example your 'tablet features' for Windows. If the Mac actually supported a tablet in that case, they would show you an item in System Preferences. A great example like this is mice/trackpads. Depending on what is actually connected to your machine, you see (if you have a Mac without a trackpad, you don't see the trackpad option - or at least it used to - my air is showing the options for a mouse right now).

To turn off specific features (say Time Machine, etc), you still have to go to each items 'control panel' if you will under System Preferences, versus one place to turn them all off. There may be tools like Onyx that let you have a bit more control over things (a review here), but this isn't really built into the OS in one place.