Is the second one Chronicles of Riddick, or were you referring to something else?

Yes, the second one is Chronicles of Riddick, which debuted in theaters last week. They're planning to do a trilogy, although I don't know if Pitch Black will count as part one of the three.

And as wolf359 pointed out, the animated prequel, Dark Fury, will be released on DVD later this week.

Also, there's an video game prequel called Escape from Butcher Bay, available only for X-Box.