The old system of seals and judgements is dead -- long live the new system. At present, a paladin's available seals have been reduced to light, wisdom, righteousness, blood/vengeance (Horde/Alliance), and corruption/martyr (Horde and Alliance's new versions of blood/vengeance, to put them on even footing, insofar as seals are concerned)...You'll notice former staple crusader is missing -- it buffed holy damage on application and your all-around damage has been buffed so you won't notice a change. Madness! Now, when you cast a judgement, it does not use up your seal -- all seals last for two minutes. Also, while you have seal of light, wisdom, and justice, their use is much more limited, because you now have three different types of judgements: light, wisdom, and justice. Regardless of which seal you use, using judgement of light, wisdom, or justice will apply the debuff formerly associated with the seal of the same name while doing the immediate effect of the seal you currently have up. It may sound convoluted, but in practice, it really cuts down on the seal/judge/seal/judge keyboard action and streamlines paladin combat.
Update: Clarified the new corruption and martyr seals which, as many commenters have pointed out, are versions of blood/vengeance for the opposite faction. Also, I'm a total idiot and forgot to mention righteousness. It's not gone, I promise!
More questions after the break..!