A chaotic neutral character follows his whims. He is an individualist first and last. He values his own liberty but doesn't strive to protect others' freedom. He avoids authority, resents restrictions, and challenges traditions. A chaotic neutral character does not intentionally disrupt organizations as part of a campaign of anarchy. To do so, he would have to be motivated either by good (and a desire to liberate others) or evil (and a desire to make those different from himself suffer). A chaotic neutral character may be unpredictable, but his behavior is not totally random. He is not as likely to jump off a bridge as to cross it.
As an example Gimble, a bard who wanders the land living by his wits, is chaotic neutral. Chaotic neutral is the alignment which represents true freedom from both society's restrictions and a dogooder's zeal.
Chaotic neutral characters often believe that there is no order to anything, even their own actions. With this as a guiding principle, they tend to follow whatever whim strikes them at the moment. Good and evil are irrelevant when making a decision. Chaotic neutral characters are extremely difficult to deal with. Such characters have been known to cheerfully and for no apparent purpose gamble everything they have on the roll of a single die. They are almost totally unreliable. In fact, the only reliable thing about them is that they cannot be relied upon! This alignment is perhaps the most difficult to play. Lunatics and madmen tend toward chaotic neutral behavior.
The outer plane of Limbo (and to an extent, Ysgard and Pandemonium) embodies this concept.