I used to love 24, but last season's torture-porn outing kind of turned me off from the series. Lately, I've been re-watching some of the seasons on DVD and I think I figured out where they should go from here - Jack Bauer should become the villain. Let's face it, they guy's been pushed over the edge far too many times to remain mentally balanced, and this would give us a villain we could finally get into the head of, instead of our usual Mulim/Russian/Bauer-family-member that are about as deep as cardboard cut-outs.
Here's how I'd plot it out. Evil asshole VP Powers Boothe is now President (I realize he ended last season seeming not to be as big of an asshole as we thought, but run with me - this would also work with Pres. Sherri Palmer). During another investigation, it comes to the attention of someone in CTU that he (asshole former VP, now known as AHFVP) may have been involved with Pres. Palmer's assassination. Someone in CTU (ie. Chole or Audrey) relays this info to Jack while he's on somewhere washing dishes and generally living the life of a crazy-hermit. At this point, Chole/Audrey is killed by someone close to the AHFVP for relaying this info. From this point on, Jack Bauer decides that the President must die. I would frame this all happening one day in New York city where the Pres. is making a campaign appearance. During the same day, CTU is in NYC making the afforementioned terror bust. After his friend's death, Jack makes it clear to someone in CTU (Buchanan? I know he's out, maybe Jack can call him for advice) what he's going to do. From there on, it's a cat and mouse chase through New York with CTU trying to stop the assassination, following up on the info about the VP themselves, trying to keep it from other gov't agencies that one of "their own" has gone rogue , along with a possible pararllell assassination plot from another faction. I think this would be great. It'd give us a great villain, give us a reason to stop all the damn torture, plus, whoever is hunting Bauer could be set up as a future 24 hero should the series continue without Sutherland. Fox, send me a damn check!