Just a topic for everyone who stumbled upon a secret, found a great solution to a quest or an easter egg.

I'll just begin:

(1) From the prison in the druid's grove you can jump, at its backside, to a rocky path. This leads to an underground passage with a fight, leading out of the grove.
But before going into that passage you can also go on and come to the backside of the 'pantry'. If you have the wizard's teleportation you can teleport into that and heal some character in there who says you should not be here.

(2) At the shore of the druids grove you can rescue a boy from some harpies. But you can go on around the harpies' rock and jump several rocks ahead to reach their nest for some loot.

(3) If you enter the 'sunlit wetlands' there is apparently some kind of magic check. If you pass it, it transforms into a swamp.
The best way to deal with Ethel seems to be to 'leave' and then corner and attack her. If she becomes invisible, you can use area effects to make her visible again. This is far easier than the fight in her cave. If you defeat her you can also speak to one of the masks (mask of regret) who will invite you to visit her inn in baldur's gate.
I don't know whether you get anything better/more if you take the harder fight.

Very important: You can place larger items on vents to block them. *Always* block vents ;)

1 there are 3 different ways into that area but only 1 makes it easy to save that druid
a thief can just walk into the pantry from the front door... save first because the cut scene is very buggy
2 you can only save the boy if you do this fight before the party happens
3 yes and no, there are extra story bits but loot is the same assuming you still look around all the areas

the area above where you find Shadowheart is the best way into the fort she wants to open.
hint
two guys are standing right under a big brick held up with rope... sure would be a shame if something happens to that rope