You already know about this, so I won't waste your time. (I haven't read the other bloggers on this as of yet.) The question is what it means: both politically, and strategically.
(One observation is obvious: the Iraqis will be overjoyed about this, and well they should. They needed their demon exorcised, and now they can finally stop looking over their shoulders.)
Strategically, this will help the U.S. to finally ascertain the exact nature of the Iraqi resistance- or should, if they play it right. Most of the speculation in the media has been that this will cause a short-term increase in terrorist attacks, followed by a rapid decline as Saddam loyalists are forced to deal with the reality that he's gone. This will likely be true, if the attacks really are motivated by loyalism to Saddam and not to another figure (such as the clerics or Bin Laden); if they are motivated by sheer hatred of the Americans, then it's unlikely that they'll cease. If they don't, then that's the clearest indication yet that resistance is not tied to any wish for a return to Saddam's regime but to the Americans themselves. If that is the case, then they have a much harder job ahead of them, as they will have lost their Snowball.
(Note that there may well be some crossover here- Saddam likely was responsible for the caches, but there's no guarantee that it's only loyalists using them).
In addition, the odd circumstances of Saddam's capture and his calm, cooperative behavior will have real effects. I'm not quite sure, however, whether it'll be seen as a massive embarassment for anti-U.S. forces or not. It may well drive people into Bin Laden's camp, simply because he has not been captured yet, and because Saddam's capture is certainly a blow to secular pan-Arabism.
Politically, one can divide the real results into left and right, Democrat and Republican. The Republicans, naturally, will gain huge morale and argumentative power after this, and Bush's popularity will certainly increase. I had predicted this earlier- the so-called "third bounce" that I had been waiting for since the war ended. This is likely to be the last bounce, however, unless they capture Osama, which has proven itself to be a much more difficult job. (Or impossible, if he's buried under rock at Tora Bora.) I expect that Bush's ratings will get a massive boost after today's speech, possibly 15-20%. The question is whether he can retain that, and that goes back to the strategic question I mentioned earlier. Without Saddam to pin the resistance on, Bush is in a position where he absolutely needs resistance to die down, or else Americans will start seeing Iraq as an intractable problem that cannot be solved by finding and killing the supposed "mastermind". The personalization of this aids Bush right now, but may hurt him later. If the resistance does die down, though, Bush is in an excellent position, especially if the economy continues to improve.
The Democrats, on the other hand, face a huge test. Now, if the candidate were smart, they should have been wargaming this from the very beginning of the runup to war. This was entirely predictable, and if they didn't predict it, they're dumber than Bush has ever been accused of being. I can't have been the only one who saw the third bounce on its way.
One candidate was already all over this, and was in an AMAZING position to exploit this: Joe Lieberman, whose performance on Meet the Press may well reactivate his candidacy in the eyes of the press. If the resistance dies down, it's likely that Democrats will return to the "support the war, not the president" tactics that characterized them in 2002 and early 2003, and that aids Lieberman.
Everybody else is in a bind of a sort. Most will probably walk the line, but it's clear from both MtP and the reactions from other news outlets that all eyes are on Dean. He opposed the war, if not the proper conclusion of it, and he will will be asked some difficult questions. Lieberman was hammering over and over again on one simple line: "if Dean had his way, Saddam would be in a palace, instead of a prison". (It's pretty clear that Lieberman knew what to do when this happened.) Dean needs to respond to that, and respond quickly and well. If not, then his candidacy will be damaged, perhaps fatally. What should he say? I'm not sure- I'm not Dean or Trippi. Like I said, though, they'd be absolute idiots not to have seen this coming, and their sound bite on this should have been fully developed months ago.
One final thing: the dealbreaker here could be the trial. This is a surprise- I wasn't expecting the Americans to take Saddam alive. The Iraqis want a trial in Iraq, but the Americans may not oblige. If they don't, this could be an enormous source of tension between them and the Iraqis. If they do, then the "coalition" and potential Iraqi investors may scream about kangaroo courts, and anti-American groups will say that Bush's puppets in the IGC were just doing their master's bidding and getting their master's revenge. It could further alienate the Islamic world from the United States, and nobody needs that.