And I quote

Russell's paradox is the most famous of the logical or set-theoretical paradoxes. The paradox arises within naive set theory by considering the set of all sets that are not members of themselves. Such a set appears to be a member of itself if and only if it is not a member of itself, hence the paradox.
While I have understood this, I was wondering of some examples of "sets of sets which are not members of themselves."

Off the top of my head, {NULL} would be an example. Is this correct? (How do I type that null symbol, where's NoteMe when you need him? )

Can I see more examples of such sets?