Of the popular ones in WCW, basically everyone that doesn't have good terms with the WWF are gone. Guys like Jeff Jarrett, Dustin Rhodes, and Goldberg. Goldberg is still enjoying his "retirement plan" with paychecks from Time Warner, but once that expires he may be back in the WWF.
And not really related, but other big name guys that are currently injured and won't be back for a little while are: Chris Benoit, Triple H, and Scott Steiner.