Last thread involved a Paladin getting intimidated by an evil party of monster pcs. Paladin now intimidated becomes "friendly" toward the party for 10-60 minutes.
With Diplomacy (and Intimidate) it's important not to overstate the effect. Otherwise, these two skills can become game-breaking in their potency.
In general, I would go for a "friend of a friend" analogy - imagine you had just been introduced to a friend of a friend. In this case, you would be
friendly towards this person, but you wouldn't yet be
friends, right? Now, imagine what you might do for such a person, and imagine also what you
wouldn't do. (My guess is that you would probably be happy to converse with them, might offer some advice, but would stop short of giving up any significant amount of time for them, wouldn't lend them money, and
certainly wouldn't do anything illegal for them.)
That's the effect of a single successful Diplomacy or Intimidate check.
Now, there are two other factors at play as well. Firstly, there is the possibility of a sweetener - for Diplomacy this would be a gift or bribe, for Intimidate the threat of torture (or, in the case of the Paladin, the torture of someone else). This swings things, potentially significantly - if the friend of a friend can offer a big enough boon in turn, what you would do for them is likewise increased.
Secondly, there is the possibility that through continued acquaintance (repeated Diplomacy or Intimidate checks), the "friend of a friend" may become simply a "friend", and in that case it's likely you would do more for them. But that's a longer-term proposition, not merely a matter of a single check.
Is the effect of intimidate strong enough to get the Paladin to reveal town defenses and such to the evil party knowing full well it will endanger the lives of the people he has sworn to protect?
No. Note that the
charm person spell states that if you order the target to do something he wouldn't normally do, you have to make an opposed Cha check. Intimidate, being non-magical, should be less potent than that - your attempt automatically fails. (Again, unless you can throw in a sweetener.)
(If entrusted with confidential information, by an employer or similar, you wouldn't reveal it to a friend of a friend. Heck, you generally wouldn't reveal it to a
friend. Although given sufficient incentive, you might.)
Or does it just take him down to willful conversation where he would then try to bluff as much as possible to lead the evil party astray/minimize the damage they could do?
I don't think so. In fact, I would have said that it was an
unsuccessful Intimidate check that would result in an attempt to deceive. I would expect the intimidated Paladin to simply say nothing about those areas where he can't reveal the truth.