When should I be using IDisposable, is it ever wrong to use it? What about Dispose Chaining?

I'm really looking for some best practice wisdom. So here are the questions, I'll add more if people leave comments. Feel free to answer some or all of these questions.

When SHOULD I use IDisposable? Only when I have unmanaged resources?

What variations of the dispose pattern are there and why do they vary?

What are common unmanaged resources I should be aware of?

Is it ever wrong or misleading to implement IDisposable?

Should Dispose calls ever be chained together, or should we rely on using statements? For instance:

public Dispose(bool disposing)
{
  ...
  this.SomeDependency.Dispose;
}