There are no anti-spyware/adware apps that I'm aware off. But then, for OS X, that sounds like a solution in search of a problem.
As for utilities... Onyx and MainMenu are the two most popular freebies.
As for defragging... the OS does that automatically for smaller files. There is a very good defragger called iDefrag that can do a more thorough job, but isn't something that you'd need to use regularly, if at all.
A little more on defrag:
Most will tell you it is not necessary at all with OS X.
Even the tech experts I've read that believe it is necessary, typically do not use/recommend a defragger until a combination of a couple of things occur. 1) The disk is 80% full and 2) You're moving around large files (GB and larger).
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