Fighter - Becoming lord of Nalia's keep. I've "done" this one a couple of times, but I've never played the game long enough (in game time) to see it to the end. I think Isaea Ronell (sp?) is behind the troll invasion but I'm unsure. Is it worth hanging around for?
Ranger - ? if I had to guess I'd say it would be in the Umar hills, since their ranger died.
Paladin - I thought it was pretty cool being in the Order, but I think it would've been better if the quests weren't all the "do it now!" types. That's the nice thing about Nalia's keep and the Planar sphere... they aren't just one-shot deals. Side question about alignments: should a lawful good character side with the baron? Lawful/neutral/chaotic good don't seem all that different to me. What kind of situation would characters of these respective alignments to act differently?
Cleric - ? Presumably something to do with the temple you're aligned with (if you have a kit). If you don't have a kit I'm not sure.
Druid - ? This one is pretty obvious. Can you challenge for leadership of the druid grove? Do you have to be at least level 14?
Mage - Ownership of the Planar sphere. The only thing I have against this is that you don't get it if you're trusting of Lavok.
Theif - ? Shadow theives? Hard to belive that there can be MORE quests related to theives though
Harpers - ? They seem to be the only bard organization.
Monk/Sorcerer/Barbarian - ???
I guess I'm really just looking for motivation to expand my horizons ... slaughering everything with a dual-classed Kensai/Mage was the first time but I'm sure it will get old