Was wondering if I give my extra key and fob away if that could be reprogrammed to work on another rx-8?

go to this

You need a mazda key which has a chip for your ignition. Like people buying the RX-8 coloured key.

http://www.rx8club.com/showthread.php?s=&threadid=15244&highlight=DIY+code+key

I was just wondering I can clear my current key, and give as a blank to someone.

It won't be blank, it always has its own internal 'number', but that number can be accepted by another '8, by using Mr. Takahashi's procedure....
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doc

I wonder how you remove a key code from the system...

Why? That would mean no immobilizer... I doubt it is wise.

The key code is "imprinted" in your ignition system each of us has a special code. Permitted to write only by recongising the original key x 2. I think it is a clever system.